Please Welcome to the Stage: Every Single Surprise Taylor Swift Guest

Who?! Don't even pretend like you're not familiar with Nelly. If you've ever jammed out to "Hot in Herre," we know you're already excited.

Where?! At Taylor's stop in St. Louis, MI.

Why?! It's less random than you think. Taylor revealed on her Instagram that Nelly has been a guest on her last three tours, and that they're "old friends."