Pinkie Pie to You:

Pinkie Pie stuck her muzzle-less head through the closing iris at the end of the episode, intent on calling the viewer's attention to it. She knew that if she could get their attention, it would be fixed before the next episode. In the land of television, the status quo is god, after all.

What she didn't expect was that the closing iris was only two dimensional, and thus really, really sharp.

Elizabeth's grin evaporated instantly when Pinkie's severed head landed on the floor in front of her TV.