Kevin Spacey always comes across very well in interviews. He’s intelligent, funny, erudite, and, above all, an extremely nice guy.
He’s also rather good at doing impressions of famous people, as evidenced by this video showing Jimmy Fallon and Kevin Spacey having an impersonation-off using the Wheel Of Impressions.
The pair impersonate Johnny Carson, Dr. Phil, Christopher Walken, Michael Caine, and Bill Clinton, and do a great job with all of them. Spacey is clearly superior to Fallon though, obviously.
The cynic in me suggests the celebrities weren’t chosen at random, and the pair knew the subjects ahead of time so that they could write and rehearse a funny line. Still, it’s a funny clip, and that’s all that really matters.