Advise on a design issue

I've had some preliminary art work done and while I like it, I feel something doesn't sit right - it's of a series of animals, sketched, but the proportions make them all look stupid.

Don't know if this is just in my head, but I would love someone to take a look at them for a few hours and just explain to me why they aren't working as a 'group'. No redrawing or anything like that - just hoping for a few relevant comments.

Odd request I know, any advice would be appreciated.

Thanks