simon-cowell-bday-tp.jpg

If he can handle the news that he knocked up his (former) best friend's wife, this shouldn't be that hard to swallow!

On Monday Simon Cowell celebrated his 54th birthday, and when X17 photographers rolled by the music mogul's Beverly Hills home, they noticed that there was quite a bit of toilet paper all over the trees and gate outside the property. Apparently the ladies from Fifth Harmony 'fessed up to the crime and also left their boss a banner that read, "Happy 87th Birthday Simon!"

(Fifth Harmony is an all-girl group that Simon signed to his label after the last season of the X Factor ... hopefully Simon thought this joke was as funny as they did!)