DrCarrot

So I've been trying all day practically and I can't get it to look like the one pictured. It's absolutely infuriating. Surprised there's no tutorial for this, given that it appears to be an extremely common thing to do.

Thanks for this. I've managed to get the face onto the biscuit but I can't seem to get it as clear as the image show here, driving me mad! Any suggestions?

I've used paint.net for a year or so now, no arty stuff just mainly messing around splicing pics together. I have never been able to figure out how to do something like the pic below though. I mean I can get in the rough area of it but never quite as good as this. What do you even call this? Morphing? I've searched for tutorials on it but can't find any. I'm sure it's not massively difficult to do but I just can't figure it out! Thanks.