Generally, when a large variety of animals appear in a scene together, like the animals rallying in the woods, the individual species were filmed separately using a technique called motion control. A camera was set up and ran continuously as animals of each species were brought into the scene and placed on their mark by a trainer, then removed so that the next species could be set into position. When editing was complete the scene appears as if the camera was merely panning a single area filled with all manner of wildlife, standing in harmony at their union meeting.
When Archie gets tranqulized and falls down unconcious, no real bear was used. A stuntman in bear suit actually doubled for Archie.
Dr Dolittle tells his daughter that "crickets are nature's thermometer" and you can tell the temperature by their chirping. According to the Farmer's Almanac, if you count the chirps for 14 seconds and then add 40 to that number, you will have the temperature in Fahrenheit. Count the chirps for 25 seconds, divide by 3 and then add 4 for the temperature in Celsius.
Steve Zahn is the voice of Archie the Bear. He later co-starred with Eddie Murphy in École paternelle (2003). He previously appeared on Friends (1994) as the gay ice dancer ex-husband of Phoebe (Lisa Kudrow). Kudrow plays the voice of Archie the Bear's love interest Ava the Bear.
When Dr. Dolittle drives with Joey the raccoon to the woods for a meeting with the head of the animals union, THE Boss, "Don", the Godbeaver. Joey rides in the passenger seat of the car and along for the ride in the back seat is the small opossum fastened into a child's car seat. Joey jumps out of the car and follows Dolittle. Trainers carefully secured the opossum in the car seat and the raccoon sat comfortably on the passenger seat of the car. The trainer hid in the back seat and a green screen was used, which meant the car never actually moved. The trainer released the raccoon from the front seat and it followed Dolittle out of the car and into the woods where another trainer retrieved it and rewarded it with a treat.
Freckles: who played Pongo in Les 101 Dalmatiens (1996) and the sequel, 102 Dalmatiens (2000) makes a brief cameo as one of the animals that go on strike.