I like number 4 - just saying :)
yeah I think 4 is the best so far. The others might be a bit too.... rubber? like they might animate in a way they have so many wobbles back and forth because they're made of bendy rubber :P not sure if I can explain what I mean here without doing the actions in person :)
I would have to say I agree with the above two statements. Number 4 looks the least rubbery. I also like the idea of the smaller eyes as just dots instead of large, rounded eyes.