I’ve worked in doing Matt Damon before…Casey wouldn’t be too hard.
There was an episode of CSI where Grissom was investigating a crime in which one such “actor” was a suspect.
My favorite line in that episode, so far as I remember it: “Cary Grant was a movie star. Gary Cooper was a movie star. He’s no movie star.”
Countless millions have said I’ll be back in Arnold’s voice. It might be the most impersonated one-liner of all time.
In a sense, all Rock n Rollers are doing a Chuck Berry impersonation.
My favorite “too soon” joke involved a celebrity impersonator. Vaughn Meader was very famous in the 60s for his John Kennedy impression. He did a comedy album called “The First Family” that was so popular (7million copes sold) that JFK used to give them out as Christmas gifts. Anyway, on November 22, 1963, the world was shocked by JFK’s assassination. Comedian Lenny Bruce went on with his scheduled show just a few hours later. Bruce walked onstage, stood silently for several moments, then said sadly, “Boy, is Vaughn Meader fucked.”
The OP’s examples (Nicholson, Walken) are usually done as just voices, IME.
The extra joke in the scene is that Cruise is doing that impression for Kevin Pollak, who did a Jack Nicholson impression as part of his stand-up act.
Johnny Carson: That is wild and whacky stuff.
Sorry, just brainstorming on common things people sometimes say. I’ll return for more once I give it more thought.
Not a celebrity but a famous character. Homer Simpson’s D’oh! is probably going to be the only catch-phrase that will outlast the Simpsons. Its short and snappy enough to be used without deliberate intent. Perhaps that disqualifies it as a celebrity impersonation, its just become part of normal language?
Elvis Presley and it’s not even close. No one is in second place.
That’s really quite ridiculous. All movie stars have always been somewhat similar - that is why they are movie stars - but many have had distinguishing characteristics.
If you are literally saying Matthew McConaghey, Tom Hanks, Jennifer Lawrence, John Malkovich, Samuel L. Jackson, Jeff Goldblum, Woody Harrelson, Scarlett Johansson, Adam Driver and Dwayne “The Rock” Johnson aren’t rather distinguishable and impression-ready I can only conclude you don’t go to the movies much.
Carol Channing. Having met and talked to her, I am amazed at how unique her voice really was, and how the impersonators did not get it right.
I agree that Bette Davis was one of the most impersonated of celebrities (and one of the greatest actors of all time). Interestingly, one of her most iconic lines, *“what a dump” *from Beyond the Forest is most remembered and imitated as Elizabeth Taylor delivered the line in Who’s Afraid of Virginia Woolf. Bette’s original version was low key; Elizabeth’s was over the top (but fun).
For you young people who may be unfamiliar: watch Who’s Afraid of Virginia Woolf. A great film and, in my opinion Liz Taylor’s finest performance (Sandy Dennis was excellent, too). Then,fasten your seat-belts and watch every film Bette Davis starred in—that woman had the best acting chops in the business.
Pollak has a hilarious act in which he does famous actors playing Star Trek characters. He plays William Shatner, Robin Williams as Chekov, Christopher Lloyd as Mr. Spock, Jack Nicholson as McCoy, and Dudley Moore doing his Arthur character as Scotty.
Howard Cosell was often imitated. Rich Little’s head will still be doing him in the 31st century. 
Walter Cronkite was imitated quite a bit, too.
Wow. There’s something nuclear-powered about her - had to use her glass-shattering mug for an avatar at a hockey website.
Not frequently imitated, but Alan Thicke and Mike Wallace in the hands of Harry Shearer is a special thing.
And they all had to at least take a shot at doingHillary Clinton.