Cheech and Chong Nice Dreams (1981)

Superlative stoners Cheech (Cheech Marin) and Chong (Tommy Chong) realize that one of their pals is developing a strain of pot that slowly morphs smokers into reptiles. They begin hawking the one-of-a-kind grass while disguised as ice-cream sellers, but the police, led by Sgt. Stedanko (Stacy Keach), are rather suspicious of the operation. When Stedanko manages to sneak some "ice cream" from the boys and promptly sprouts a forked tongue, Cheech and Chong must go on the lam.