I saw a mopbucket cake here on CC and there weren't any instructions with it. Does anyone know how many cake mixes it will take. Its the yellow one with the handle on the side of it and a mop handle sticking out of it.

This one?
http://cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1316447

That depends on # of servings needed.

If I were making this cake, I would use three 8 inch squares for the bottom "bucket" part and three 4 inch squares for the top "wringer" part. That would be approximately 4 cake mixes.

And of course, that depends on which brand of mix you use.

And people think making cakes is easy!