For this prank, you'll need a tube of your mum's fave crisps and a kitchen roll tube.
Empty the crisps from their tube.
Cut the kitchen roll tube so it's just a little bit shorter than the crisp tube.
Put the kitchen roll tube in the crisp tube and stack two or three crisps on top. It will look like the tube is full!
When your mum pops, she'll have to stop - because there are hardly any crisps left! Ha-ha!