Off With Her Head!

*coughs* Ahem. Now that I've gotten the cliché joke out of my system we'll get on with learning how to behead a pony.

Tools

Directions

A large majority of pony heads will come off just by pulling with minor effort. Generally you should try the back of the neck first since I've found that to be the place where you have the best leverage.
Grab the rump with one hand, the head in the other hand and bend backwards as hard as you can. If you don't at least make a crack in the seam (You may have to push very hard) then try other spots.
If the head comes off with this method then you are done and can skip the rest of this page.

If none of the neck will give way you have to use method #2....the X-acto.
HHHHHHHHHHHHH
First and foremost I would like to stress the importance of safety when using and X-acto. They are very sharp (I have a couple of scars from slip-ups myself). Don't not use a large amount of force when cutting with these things. Large force = stored energy, which, if you slip = released energy which equals you running around the room screaming like a small child while you get little red dots all over the carpet. Or, if you're like me, you mutter naughty words under your breath, stomp off to the medicine cabinet to get a band-aid and then go right back to work.
Anyhoo. Take the X-acto and with the blade turned backwards (Pony plastic is pretty soft so just the tip will do) slowly scratch away at the seam line.
If the pony seems particularly stubborn you can use the edge of the blade; just be extra careful. Once you have a small crack try method #1 again. It may come off now.
However, if the pony decides to be evil you'll just have to keep alternating between method #1 and #2 untill the head comes off. On occasion you will just hafta cut the sucker off completely, which is no big deal. Zap-a-Gap (See tools list) will take care of it nicely once you're ready to reassemble your pony. Use the X-acto to cut out the part of the 'neck plug' left in the body. Just run the blade between the neck and the neck plug. It shouldn't be too hard.

And now that you've complete this gruesome task:
On to step 2!