Ripplin said:

I think it might look a little less puppety by leaving it as is, but maybe slowing it down a tad more and maybe showing some dust/debris/whatever flying out around its mouth as it slams shut. The scene has never bothered me, but I know Ady will do something to it in the usual subtle, logical way. :)

Yes, I think that the speed of the action is a major part of the puppet feeling. Like the old movies with little boat models on big waves. Here we "see" the human hand behind the slug.

Prior to adding new teeth this scene needs indeed a treatment to make it looks more real in scale.