This is more classically known as the "I'm going to get my big brother to beat you up" syndrome, when a player brings in a higher level character to handle a problem for a lower level character. You can try, as many have, to explain just how it was that Big Brother Billy knew that Little Brother Bobby was in trouble at that exact time, and how Little Brother Bobby conveniently disappeared while Big Billy came in and solved Little Bobby's problem. It will give us a laugh as we delete the offending characters. This includes sending Bobby out on a revenge-mission later. Bad idea.