It's been four years since Donald Trump, then a long-shot candidate, appeared on The Late Show with Stephen Colbert just two weeks after its launch. When CNN's Anderson Cooper asked Colbert if he'd welcome the president back, Colbert responded: "The quick answer would be no, because it would be hard for me to be properly respectful of the office. Because I think that he is so disrespectful of the office. It’s very hard to perceive him in the way that I would want to perceive a president in terms of their status and the dignity and representation of the United States. So I think just for safety sake, it wouldn’t be a good idea."