I was tiiiired last night. Mommy was doing homework on the bed and I rolled over (as shown). She couldn't resist. She googled "sideways head" and didn't come up with anything, and then tried to think of what already had a sideways head...not a cow, not a horse, not even a cool lizard, but a fish. Gee, thanks, Mom.
(note from Mommy - this was in no way set up, and he stayed like this long enough for me to search google images and get off the bed to grab my camera)