Have a long shower, create a puddle on the floor and leave the window shut.
'Forget' to close windows when leaving their house when no one is at home.
Find their hidden chocolate stash and eat it 
Ask them to cook me a meal then don't eat it, tell them to put it in the fridge and I'll eat it the next day. Never eat said meal.
Ask for lifts at extremely short notice and make them feel guilty they can't do it as they're working.
Drink straight out of the milk carton and put it back in the fridge empty.
Come in at stupid o clock, turn on all the lights and have my phone on loudspeaker mode playing TikTok when I come up the stairs.
Take over the bathroom for a really long poo then leave the loo dirty 🤢
Stay overnight and play on the Xbox shouting and swearing in the middle of the night.
Can you tell I've got a 21yo DS? 