When you're on the road for a few weeks you tend to play pranks on each other. And they're only funny if you aren't the victim. And they probably aren't funny anyway, but you know me, I got OPD*:
Setup: The bass player wipes the neck and strings down on his fretless bass with a rag containing WD40 before each set so he can glis smoothly.
The drummer wipes his sticks and hands with an astringent rag before each set for a better grip.
Prank: Swap the rags just before they go on.
Fun part: Look innocent as the bass player skids between muffed notes while dodging the drummer's flying 5b sticks as they shoot into the house.
Extra fun part: Look even more innocent while they blame it on the stage manager!
(Maybe you had to be there;-)
*Obsessive Prank Disorder