Science jokes are only funny when there's any logic to them.

Several years ago my sister had a summer party for our grown-up friends and part of it was a squirt-gun fight. While everyone was filling their guns with cold water from the hose I went inside and filled mine with warm water from the kitchen faucet. Then when I squirted someone they would go, "Ha ha! Wait..., what? OH!" I always try to do something fun and different to surprise people lol.