Oh I have some ideas~
1. Unplug EVERYTHING, if the cords are detachable, hide them
2. Music, game and movie Disks. Place them all in the wrong boxes and scratch the shit out of them. If a music CD fits in a movie box or game box and vice versa, even better.
3. Get any and all remotes. Tuck them in really obscure places.
4. Dump any Lego I may find on the floor. Break any models, excluding anything complicated or expensive (e.g a spaceship or an extremely detailed helmet.). Scramble the pieces.
5. Take anything fragile, place them in really bad spots, like behind doors. Nowhere anyone could get seriously hurt like under a pillow.
6. Re-arrange any laundry they have in their cupboard.
7. Turn random objects upside down. Any and all
8. Scramble the placement of chairs. Place a recliner at the dining table, and a stool in the living room.
9. Alter the languages on any and all electronic devices. If they left device unlocked, change the password to keyboard smash including random capitalisation and symbols and then encrypt it using a one-time pad.
10. Turn on all the lights in every room, all the fans, AC, etc.
11. If I have access, crank Kids Bop on loop and hide the controls.
12. Take one sock from each pair and hide them elsewhere in the house.
13. Feed any pets they may have. Nothing malicious here, just making sure they’re taken care of.
14. Shit in their sink/pillowcase/bed
15. Hide a replica horse head in the bed/s, slosh some fake blood over that to really sell it.
16. Dump flour on the ground.
17. Dump syrup on the ground.
18. Dump feathers on the ground.
19. Turn a wall into a Jackson Polluck painting.
20. Put those little poppers under the toilet seats.
I have more but this is already over three hundred words, so I think I’ve made my point.