The X-Factor judge got one up on his co-star after she teased him about his age last year on his own birthday.
High in the sky above Cheryl's Las Vegas hotel this week, an aeroplane skywriter scrawled the message, "Cheryl - Congratulations. You're 30 next year! Ha ha ha."
The message isn't as 'Simon Cowell nasty' as it sounds, though. Cheryl delivered a similar birthday greeting to Simon last year, hiring an aeroplane to drag a banner reading, "Simon Cowell is 52 today! Ha ha ha! Love Cheryl."
Oh, you two!