Girls just want to have fun!
Their latest stop was Denver, Colorado. That's when the two co-judges decided to pull a prank on Simon Cowell!
They served him up a local delicacy called Rocky Mountain oysters - otherwise known as BULL TESTICLES!
But Simon still wanted to have a little fun of his own!
He then offered up the gross grub to Paulina Rubio!
Poor Paulina! We hope she didn't fall for it!
Ch-ch-check out a shot of the tasty testicles below!
[Image via Dennis Van Tine/Future Image/WENN.]