It looks like young Keith Gridley will have a lonely summer, until he meets a talking mouse named Ralph. Ralph takes an immediate liking to Keith's toy motorcycle and can ride it just by making a motor noise. Ralph even acts heroically when Keith comes down with a nasty fever, while dodging cats, owls and a guest's noisy dog.
| Actor | Role |
|---|---|
 Philip WallerKeith Gridley | Keith Gridley |
 Mimi KennedyMrs. Gridley | Mrs. Gridley |
 Thom SharpFrank Gridley | Frank Gridley |
 John BynerGuest with Dog | Guest with Dog |
 Ray WalstonMatt | Matt |
 Mary Jo CatlettKindergarten Teacher | Kindergarten Teacher |
 Evan RichardsRalph (voice) | Ralph (voice) |
 Zelda RubinsteinRalph's Mother (voice) | Ralph's Mother (voice) |
 Billy BartyUncle Lester (voice) | Uncle Lester (voice) |
 Keri HoulihanSusie (voice) | Susie (voice) |
 Heidi KozakThe Maid | The Maid |