Is there a way to dislocate the jaw for genesis 2 or 3? i'm trying to make the mouth open unrealistically wide.. I tried the deform tool but it drags the toungue with the bottom part of the jaw...

Have you tried turning off the "Use Limits" parameter for the mouth open and mouth open wide morphs?

Yep it just distorts really bad...

The tongue is attached to the lower part of the jaw in reality, surely, so you would expect it to move with the jaw.

I don't think there is a way to do that. I just spent about half an hour trying every option I could think of, but there isn't anything that works. Abut all I can suggest is, if you have modeling skills, to try to make a morph for that and add it to the geometry (I'm not sure exactly how to do that because, even though I do modeling, I never learned how to make morphs or add them to a figure).

wheatpenny is on the right track if you were a vendor looking to make it as a asset it would be a lot tougher. In other software but similar bone/rig structure for animated characters we would remove the jaw and bottom teeth and remod and make the bottom half a accessory/prop to attach no different than you would a hat. If you wanted to use this concept for the one image then multiple renders from same camera angle in iRay (set to render scene only) stages and a few hours in Photoshop. Background scene-Character with expression and mouth open wide with limits see if you can slide jaw to left or right just to point of distortion (more to drag face muscles in right direction) -Character with limits off and wayward tongue to be manipulated using previous image. Use combo of both and clone stamp, eye dropper 3D tools to manipulate image. basically cut and shut.

Thanks for the replies everyone, I appreciate it!!