The famous couples aren't just good friends with each other, they're also neighbours - and this has led to more than a few prank wars between them!
As Jimmy explained on his late night show, it all started when Emily and John broke into his house to light up a Christmas display inside. Before long, the pranks were getting more and more epic - one year he even arranged to have Emily and John's entire house gift wrapped!
This year, however, Emily had an even bigger surprise in store for Jimmy, which she revealed live on his talk show. She and John gift-wrapped Jimmy's car twice, filling it with festive baubles the first time and a group of Christmas carollers the second - plus a real reindeer!
For the last step of the prank, John dressed up as Santa and took Jimmy's car for a spin - all while holding onto Jimmy's personal computer and clarinet.
"I'm going to take this for a spin because I need a sleigh to give away all your stuff," John joked.
"You're freaking out right now and I love it."
Check out the prank below: