The Angry Beavers (1997)

S4E15 Van-tastic Voyage

In a wild scientific escapade, Scientist #1 and Pete accidentally transform Dag into a gigantic version of himself, allowing them to navigate their plush custom van through his massive form in search of the mysteries behind the pointy weasel creatures. Norb finds himself tasked with the challenge of halting their reckless experiment and restoring his brother to his original size before things spiral further out of control.