I play a dwarf monk with a drunken fist homebrew path in my current regular game. Our party is currently level 4. Another player is a Goliath Artificer, and we've gotten into a prank war. Currently we are taking a 2 month break in game, and I was wanting to play a long game prank on him. I came up with some stuff, but he has so far stymied me since all he has done is tinker, research, and try to imprint himself on our baby tarrasque. Oh yeah, we have a baby tarrasque....

Anyway, I don't want to do anything that could kill him, and were kind of in the middle of nowhere deep in the woods with not a lot of people around. We have a rogue in the party, but she's spent all of her time in a town a couple days ride from us. We also have a druid, but so far nobody knows where she is or what she's doing. All my ideas involved hiring people from town. 

Any ideas would be helpful.

What kind of pranks have you already done?

Sovereign glue on the toilet seat in the outhouse.

I was once mounted on a drawbridge while I was passed out drunk.. I was playing a rogue so you know first instinct pick this lock.. needless to say, the fall hurt but only a little bit.

I would just search google for pranks that college/university kids do to each other/professors/etc.  I am sure you can convert most of those pranks to be in-line with D&D! -)

TQQdles™