Roaden Polynice
Superstar
It's super telling how much the industry has changed that Jerry Lewis wanted De Niro to kill him in the end, as he felt the way it did end really lacked a "finish". I imagine everyone from Jerry's era of entertainment saw stuff like that and was just like "what's the fukking point" whereas fast forward to now and if an ending isn't ambiguous everyone calls it cliched.
edit: spoilers?

Another good call was not making Rupert completely bomb. That would've been too easy an ending as well. Just making him mediocre with some middling and ok jokes added another dimension to the entire story. And I read Ebert's review of when it first came out and he sorta got at the ending and the movie in general in how it's so tightly wound, you're expecting there to be some sort of emotional payoff, some type of closure but it just never happens. That's part of what makes the movie somewhat hard to watch but at the same time really memorable.