Possible to hack children's toys voice chips?

Factual Questions
1

As part of an office gag, I would like to buy one of the monstrosities known as the Perfect Polly: Perfect Polly Pet - Official As Seen On TV Commercial - YouTube
and hack the sound chip to say rude comments in between the tweets. Is it possible to change the chip recording in this or other children’s talking toys, or else replace them with a chip of your own at fairly low cost?

If so, how would one do this?

2

Well, there’s this.

3

A little searching reveals plenty of similar products

4

I think this bird just has a whistle or something like that to make that noise. You could use the items suggested by Sailor and insert them on the toy. Or just use this: http://www.thinkgeek.com/product/b278/

5

They tried to teach me how to do this, but math class is hard!

6

That’s because you are blonde and have big tits.