I'll try to come up with something fancy.

-Any female character with a "long" maw. Preferably dog, but dragon or something will do.

-2 frames. On first just a normal face. Preferably in front of a cock bigger than the facehole. Female can say something like: "It won't fit!" or "I will not!" Character can be in a pillory, in chains, doesn't matter.

-On second frame, character with a dick (Or just poorly drawn hand in small window in the corner) presses a button on the remote and it opens victims mouth.

IMPORTANT: Mouth should be opened a little bit more than normally.
Mechanism inside should be visible then mouth is opened. Just a bit. Less is more.
Character should be astonished, in fear, etc.

Bonus points if neck gets stretched from inside by another mechanism.