Conversation so far:
What roles did DeVito play on television?
DeVito played the role of John 'John John the Apple' DeAppoliso in the Starsky and Hutch episode titled "The Collector".
What was some voice over work that he has done?
DeVito voiced the Grundle King in My Little Pony: The Movie while.

Question: When did he start acting on television?
Self-contained rewrite: When did Danny DeVito start acting on television?