Have you tried freezing the poor lil thing for a day or two to see if the change in temperature when you thaw it back out loosens the glue any? Alternativly, a warm water bath for a few minutes amy also help. For the freezing method, just make sure the plastic doesn't get brittle.
You might also want to grab a large container of WD-40, pour some into a bowl and let the Joke Machine sit in it for a while and see if that helps any of the areas where you have already picked some of the glue out of. Make sure to test this first on a non exposed part to make sure the WD-40 doesn't eat the paint.
Alternativly, depending on how old the glue is and how flexible the plastic is, you can try the "felt and hammer" method. Find a small ball pean hammer, and a fairly thick piece of felt. Place the felt over the glued area, then strike gently with the hammer starting in the middle and working your way outwards. This takes a bit of practice, but you should be able to break up some of the glue without damaging the plastic.
That's all that I can think of at the moment. Hope that helps!