The first time, I gave 15 lbs to a friend in another lab.
A year later, I was taking a class from friend's advisor, and it came out that I'd been responsible for the 15 lbs of sour worms that had materialized in her lab. The look I got conveyed "you... you?!? did that?"
Well, the first round caused a postdoc to fail his willpower check badly enough that round two, several years later, was met with shudders and warding signs.