Alvin and the Chipmunks Meet Frankenstein (1999)

Alvin, Simon and Theodore revel in their new gig at a movie theme park by wandering the grounds after hours. Among the attractions is the spooky Frankenstein's Castle, where a real mad scientist is bringing the monster to life. But when the boys cross paths with the creature, they soon learn that appearances can be deceiving, and Frankenstein is more misunderstood than malevolent.