Conversation so far:
When did Danny DeVito start acting?
Danny DeVito played Martini in the 1975 film One Flew Over the Cuckoo's Nest, reprising his role from the 1971 off-Broadway play of the same title.

Question: What other film roles did he have?
Self-contained rewrite: What other film roles did Danny DeVito have besides Martini in the 1975 film One Flew Over the Cuckoo's Nest?