Off the Wall

Panel 1: Mooch the cat about to throw a ball as Earl the dog waits excitedly. Panel 2: The ball in the air. Panel 3: Earl and Mooch recoiling in surprise as it bounces off the right panel border with a 'bonk'.

I got a kick out of this Mutts strip from September.

The most amusing part to me is that it doesn’t really break the fourth wall but accomplishes something very like what we think of as breaking the fourth wall by not breaking the panel’s third* wall, surprising the characters — and in turn the reader — by suddenly reneging on the contract that allows panel borders to be drawn in the same ink as lines defining solid objects within a strip’s panels yet be traversable by said objects as portals to the rest of the world being depicted.

[*While I’m not sure the other “walls” have a conventionally accepted numbering, if
you count from the left clockwise in a plane intersecting the flat page or screen (or the proscenium of the stage, from whence the concept originates) — the second/middle wall being the background, parallel to the unseen “fourth wall” through which we view the action — you end up with the left and right walls being the first and third, respectively.]