Professor Nimnul has invented a device to transmit himself across telephone wires, and uses it to steal scientific devices from guarded laboratories. A neglected Zipper discovers Nimnul in the act and is caught in the Modemizer with him, leading to two creatures out of The Fly.
- Gregg Berger - Doctor, Police Operator
- Susan Blu - Female Guard, TV Reporter
- Corey Burton - Dale, Zipper
- Peter Cullen - Officer Kirby, Officer Muldoon
- Jim Cummings - Monterey Jack, Professor Norton Nimnul, Waiter
- Tress MacNeille - Chip, Gadget, Radio Voice, Teenage Girl
- Fran Ryan - Teacher
- Final appearance of Professor Nimnul.