EVERY TIME THE CAMERAS ROLLED on the set of Mouse Hunt—the current comedy about two brothers' battle against a resourceful rodent—actor Nathan Lane made sure the movie's star was prepared. "He would call, 'Ready for your close-up, Jenny?' " says animal trainer Boone Narr. "He would act like she was this huge actress from the 1930s."

Never mind that Jenny—and her 64 furry costars—is more used to Habitrails than Hollywood. For Mouse Hunt, the creatures, thanks to Narr, 49, went where no mice had gone before: They turned on radios, dodged shooting nails and pushed traps onto a cat's tail. (A few stunts were done with computer animation.) "The early stages were 'take 100,' " says director Gore Verbinski. "By the end, they were pulling off remarkable things." Says Narr, an Aurora, Ill., native who had his pupils repeat simple tasks and rewarded them with nuts and Velveeta: "There were a lot of rejects. If they didn't like it, we didn't use them. You wanted mice with a good attitude."

Not that any critters ended up on a date with d-Con. After the movie wrapped, cast and crew adopted them, and the twice-divorced Narr (who also trains Mad About You's Murray the dog) brought two dozen to his six-acre compound in Castaic, Calif. "I love these little moneymakers," he says. "They paid the rent this year."