The old James Corden can't come to the phone right now. Why? Oh, because he's too busy being Taylor Swift [1]'s backup dancer. During a hilarious skit on The Late Late Show [2] on Thursday, the host decided to fill in as the Forum general manager during the iHeart Radio Jingle Ball [3] in LA. Aside from playing security guard for Ed Sheeran and giving Demi Lovato [4] a pep talk, he also filled in as one of the backup dancers for the "Look What You Made Me Do [5]" singer. Let's just say, Taylor instantly regrets it. See how it all goes down above.