Their SM:TV segment Challenge Ant is brought back for a one-off Keith Lemon edition and the comic star takes the opportunity to measure McPartlin's sizable forehead.
Ant is given a shock when his guess of 5cm is massively off the mark. Watch the clip below to find out the real size of the I'm A Celeb host's ever-increasing forehead.
Celebrity Juice airs tonight at 10pm on ITV2.
Watch a clip of Challenge Ant on Celebrity Juice below: