Ack! Been playing it on VBA, and...
(spoilers?)
Quite far into the game. About 11 hours (though I've been exploring and all, and using the speedup function here and there)
While trying to acquire the second beanstar piece from the artist... there's a nasty, nasty problem I ran into.
You have to get Mario full of water and then stand on these footstep prints. From there, this mad artist guy gives you a mini-tutorial on what he wants you to do (shoot water at paint to hit this dress he's making). This is all fine until you hit Mario using Luigi's hammer during this tutorial. Mario shoots the water to the side instead of the robot, the little paint robot that the water was SUPPOSED to be shot at makes faces and it loops forever like that. >_<
EDIT: Works on VBA 1.7-Beta3, but 1.7-Beta2 and on seem to crash my W98 system when I multitask >_<
Oh noes.