Although Stuart and several other characters are computer-generated (CG), including Margalo and the Falcon, many other live animals contribute to the film. The Film and TV Unit of the American Humane Association (AHA) monitored the action sequences involving animals. The AHA has sole authority, through a contract with the Screen Actors Guild, to protect animals used in film and television.

Inspectors reviewed the script and action scenes before and during filming to ensure that animals were not harmed or mistreated and that AHA Guidelines for the Safe Use of Animals in Filmed Media were upheld. They also monitor conditions in which animals were housed during production.

Little Birds

During the opening credits, birds sing in the windowsill as the camera pans around the Littles' bedroom. Mrs. Little goes to the window and opens it and the pigeons on the windowsill take flight. Four trainers prepped 12 pigeons to sit on a perch outside the window frame. Seven of the birds were placed on the perch for the shot and as all the trainers stood off-camera, one trainer waved a net and the birds took flight. The other trainers used nets to help direct the birds to the open cages nearby with food inside. All of the birds flew safely back to their trainers and were placed in their crates and brought home.

Birds fly past Stuart's school building and are on the grounds outside. Later, Margalo flies into the car that Stuart is driving and they drive along the sidewalk and through some birds that are scattered on the ground. Trainers scattered food on the ground and the birds were released from a playpen resting beside the camera. They pecked at the food on the ground while trainers stood off-camera waving some nets to make the pigeons move. The CG car was added in later, as was Stuart and Margalo, in post production. The homing pigeons were retrieved by the trainers afterwards.

Pigeons fly around a garbage barge and land on it. This was filmed in front of a blue screen. One trainer released a bird from a box, which flew to another trainer holding a box. All of the birds were boxed trained. The CG barge and garbage were added in post production.

Birds fly in formation as Stuart and Margalo watch them. Later, as the Little family leaves their balcony after watching Margalo take flight, birds are in the sky flying. These were all CGI.

Feisty Felines

The part of Snowbell was played by four different male Persian cats. Ruffy and Tuffy are called in for the stunts, while energetic Rocky was used for scenes that needed the cat to be on the move. Lucky Prince had all of the close-ups. Sassy alley-cat Monty was played by two Tabby cats named Merlin and Magoo.

Snowbell runs down the stairs and into the kitchen by the recently-dropped oatmeal. The trainer used buzzer noisemakers to cue the cat to walk to its mark. Behind the oatmeal, the trainer hid some of the cat's favorite food. Although it looks as though the cat is enjoying lapping up the spilt oatmeal, it is really munching on its favorite treats.

Snowbell sits in the doorway of the dining room and sings the song "One is the Loneliest Number." The trainer put the cat on its mark and the computer helped him sing.

Snowbell swats at a fly that has been buzzing around, then catches and eats it. Burping loudly, Snowbell walks into the house and eats from the bowl then sits and talks to Margalo, who is sitting in a basket. The trainer tied a piece of chicken to a monofilament line and waved it in front of the cat, which sat up and swatted at the piece of meat. The fly was CG. The second part of that scene was filmed separately. The trainer put the cat on its mark and used clickers to cue the cat to walk into the house. The bowl was filled with more pieces of chicken, which the kitty happily ate.

Snowbell sleeps in his bed basket. He wakes up and sits in the basket and talks to Stuart. Snowbell gets up and walks across the room as Stuart follows. A trainer put the cat in basket. The trainer continued to pet the cat until it became so relaxed, it fell asleep. The trainer then clicked the clicker and the cat awoke and popped its head up. The cat is then verbally cued to sit up while the trainer stood off-camera waving a stick to prompt the cat to look in different directions.

Snowbell follows Stuart in his tiny car and later, as Stuart struggles to control his airplane as he flies through the house, Snowbell runs throughout the house trying to escape from it. Filmed in front of a green screen, a trainer placed the cat on its mark and waved a bait stick to get the cat to walk in the direction desired. The CG plane and car were added later in post production.

Stuart's car is stopped on the sidewalk. The hood is raised and there is some smoke coming from the tiny engine of the car. Snowbell is sitting by the side of the stalled car as Stuart investigates the problem. The cat was placed on its mark by the trainer, on the side of the tiny prop car.

Snowbell and Stuart come around the corner in the alley and another cat jumps up on some crates, then jumps down. A trainer put the white cat on its mark and used a laser pointer to cue the cat to walk in a certain direction. The crates were stacked like steps and secured by the trainers beforehand. A cat was placed on top of the crates and another trainer used a laser pointer and a clicker to get the cat to look in a certain direction and jump down from the crates.

A door to a restaurant opens and several men appear, one holding a cat, Monty, in his hand. He tosses the cat out into a dumpster sitting by the door in the alley. The men go back inside and Monty emerges from the dumpster with a Chinese take-out box on his head. Monty jumps out of the dumpster and the two cats talk as Monty laughs and rolls on his back. A special platform was built by the crew and placed inside of the dumpster to reach the top. A padded tumbling mat, furniture pads, and foam were used to pad the platform so the cat had a soft landing. The trainer prepped the cat for the scene action for several weeks. Although it looks as though the actor tosses the cat without care into the dumpster, the actor used extreme care when handling the cat. Several trainers stood off-camera supervising as this scene was being filmed. A small container was used to make a hat for the cat to wear so it appeared as though he comes out of the dumpster with a Chinese take-out box on his head. Some rubber bands were fastened to the side of the box to look like noodles. After the hat was placed onto the cat's head, a piece of monofilament wire was used to gently secure the hat in place. The cat was trained to knock the hat off by itself, but a piece of monofilament was tied to it and held by the trainer off camera just in case it was needed. After being outfitted with the hat, the cat was placed back on the padded platform inside the dumpster and then stood off-camera and used a clicker to get the cat to pop its head up. For the part of the scene when Monty is laying on its back laughing, a trainer held the kitty's favorite toy above it so its paws would move as it reached towards the toy. CG effects were also used to make the cat appear as though it is laughing.

Monty stands on a trashcan in the alley and talks to Snowbell and Stuart. A trainer placed the cat on the edge of the trash can and verbally cued it to stay.

Stuart stands on Snowbell's head and talks on a pay phone. Snowbell has his front paws on some stacked phonebooks so Stuart can reach the phone. A trainer stacked a few phonebooks on the ground in front of a pay phone. The trainer put the cat on its mark with its two front paws resting on the phone books. The trainer stood off-camera using a bait stick to cue the cat to look in certain directions. This was filmed in front of a green screen and CG Stuart was added on the cat's head later.

Snowbell paces outside of a building. A trainer set the cat on it's mark and used a combination of clicker noises and food to get the cat to achieve this action.

Snowbell sits on a scaffolding with a window washer going up. The cat was put on its mark by the trainer. The scaffold went up very slowly and was only 2 feet off the ground.

Snowbell climbs up the stairs and then jumps on a paint can and talks to Margalo, who is trapped inside the can. The staircase was specially made with extra wide steps for the animals to easily and safely climb. A trainer used a laser pointer and bait stick to get the cat to walk in the desired direction. Snowball paws at the paint can and opens it and Margalo flies out. A trainer put the cat on top of the can, which hid a piece of chicken under the lid. The cat pawed at the lid and it appeared as though the cat was trying to open up the lid. A piece of monofilament was attached to the lid of the empty can and a trainer pulled on the line and the lid flipped open.

Now Snowbell is trapped inside the paint can and it rolls to the edge of the building and falls off. It gets hooked on a flag pole below and then drops to the ground in front of a tire of a car that screeches to a halt. This sequence was filmed in front of a green screen. A combination of real cats and a radio controlled stuffed cat was used. With white fur spotted inside the can as it rolls and falls, as the can stops, four cat legs poke out and walk with the can still stuck on its body. This was done using the fake cat. As the can hangs on the pole, the cat pokes its head out. Filmed in front of a blue screen, a trainer placed the cat inside the can, which was held by another trainer 2 feet off the ground. The bucket also appears to be spinning. This was accomplished by camera angles. The bucket never moved, only the camera did. The can is empty when it is tipped and fake cat was used for the falling cat who lands next to a wheel of a car that screeches to a stop. A trainer replaced a real cat with the fake one and set it on the ground.

Snowbell runs after the cab driving down the street with the Little family in it. This was filmed against a green screen so the car was not actually used when the cat was filmed. A trainer set the cat on a mark and used a clicker to get it to run in a certain direction to an awaiting trainer and treat.

Monty the cat, Stuart, and Margalo fall inside of a can. A trainer placed the cat on the edge of the trashcan and verbally cued it to stay and "dig." One end of a tube filled with fake feathers was placed in the can before filming and the other end was held by a crew member off-camera. On the director's cue, the crew member blew into the tube, which released the feathers. The cat didn't even seem to notice the feathers. The trainer retrieved the cat afterwards and rewarded it with a treat.

Snowbell comes through the crowd to look at Stuart and Margalo. Snowbell follows the Littles as they leave. A trainer placed the cat on its mark and used a bait stick to have the cat walk in the right direction. The people move out of the way as Snowbell nears Stuart and Margalo.

George, Stuart's human brother, holds Snowbell in his arms as the family stands on the balcony to say good-bye to Margalo. As family walks off, Snowbell is still in George's arms but is talking as they walk off. The trainer handed the cat to the actor who held it in his arms. The trainer stood off-camera and retrieved the cat afterwards.

Snowbell reads a menu board outside of a restaurant. A trainer put the cat on its spot while another trainer hid behind the menu board. The trainer behind the board held up some food and used a clicker to get the feline's eye line.

Snowbell enters the house through a doggie door. One trainer released the cat from behind the door while another trainer used a clicker on the other side of the door to cue it to come. As the cat approached the door, the trainer pulls a monofilament line that was attached to the flap of the doggie door and it opened. The cat went through the door to the trainer with the clicker, who then rewarded it with a treat.

The Falcon

Though CG throughout most of the film, a real falcon was used for the scenes where the falcon is in flight and for several close-up shots of the bird. The real falcon was filmed separately and inserted into the film in post production. The falcon was placed on a perch by one trainer and then verbally cued to fly to another perch where another trainer stood with some food. The bird flew right to the awaiting trainer.

Production also had a mechanical falcon puppet on hand for certain scenes. It had so many moveable parts that it took 5 puppeteers to make it work!

Canine Cameos

Some background actors walk dogs on leashes. Trainers handed the leashed dogs to the actors and stood off-camera supervising.