Anyway, load up the linked pk3 in Doom (or any other game I guess) and summon zpoisonshroom. If you have model interpolation on, it will look very screwy (the mushroom turns itself inside out as it goes through its cycle of briefly swelling and making the squeeze noise). Switch interpolation off and it will work properly. I know the poison mushroom is a little odd (I had a look at the source code and saw that it had extra stuff in there that I didn't understand) but is there a way of improving on this?
The model is in fact a fire extinguisher from Wim Sitters that I messed around with.

http://www.zen64060.zen.co.uk/shroomtest.pk3