Great care was taken to make sure the animals used in filming were not harmed. Measures taken included many trick shots, multiple cuts, and even a mechanical dog/dog suit in order to achieve scenes.
Steve Martin was the first choice to play George Newton. John Candy, Danny DeVito, Bill Murray, Dan Aykroyd, Jeff Goldblum, Rick Moranis, Chevy Chase, and Robin Williams were later considered for the part.
Joseph Gordon-Levitt's film debut. He is the kid on the right wearing a green top who gets on the school bus while Ted hides behind a tree before getting on the bus.
Charles Grodin (Mr. George Newton) was 56 at the time of filming, Bonnie Hunt (Mrs. Alice Newton) was only 29. Though no age difference between their characters is ever mentioned.