Carson and Berle
Johnny Carson on the phone sounded like some amateur who had a few beers at a party and decided to entertain everybody with his hilarious impressions.
I like J. K. Simmons, but he completely failed to evoke Milton Berle. It was as if he's never seen or heard Berle on video, and the director just told him to hold a cigar. Since so much effort was put into actors looking and sounding like the other real-life characters, not doing the same for Berle was an odd decision. Maybe it was assumed nobody under seventy would know the difference.