Hader stopped by Ellen ahead of his hosting gig this week, and dropped a couple of impromptu impressions that prove he's got this hosting thing on lock. I mean, who else do you know who can seamlessly transition from Seth Rogan (reading to pre-schoolers) to Harry Styles (talking to a personal trainer) to Jack Nicholson (running a lemonade stand) to John Oliver (at a hip-hop concert) to Elvis Presley (at a job interview) and still manage to think of jokes that are new and creative?