In the words most eloquently put by Andy Samberg: 

"Hey Bruce, look my character Jake Peralta on the show Brooklyn Nine-Nine, which is moderately successful, is obsessed with Die Hard and thinks that your character John McClane is the coolest character in the history of cinema. I, Andy Samberg, I'm a comedian, also feel that way. If you'd come be on the show, even if it's for one sentence, like cool cameo, like we bump on each other on the street and you go, 'Excuse me,' and then walk away."