Lots of free coins & mushrooms
When you first reach Hoohoo mountain, this trick is soooo helpful.
After you get through the next cave you will reach a fountain.
Use it to fill Mario and spray water at a fan contraption that is off a small bridge nearby (have Luigi jump on to Mario to spray).
It will give you a coin if you spray the fan part. It takes some patience, but if you keep doing it the machine will start to give mushrooms as well as coins.
It will give you up to 11 or so mushrooms before it starts to only dispense coins (there's no limit to the coins)....
More tricks, tips and cheats for this game are right here - Mario & Luigi: Superstar Saga cheats
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