"Stop wearing the bowl, please."

Once again, I wouldn't have thought it necessary to make such a statement, but here we were, walking to a friend's house to return her glass bowl, and my son decides to wear it. At first, I give him 'the look' and he immediately takes it off so I think we're fine. But then I hear my daughter giggling so I turn around to see the bowl on my son's head again. Now, at this point my son doesn't realize that I see him, so when I make my remark and he turns around, he's still got a goofy smile on his face and the glass bowl on his head. I have to admit, it was pretty funny so I try and stifle a laugh while still trying to look serious, but that's not working out so well so I just abandon the whole I'm-the-parent-here-so-I-can't-think-this-is-funny act and go ahead and laugh with them. I do, however, insist on keeping the bowl off the head due to sanitary reasons and my son reluctantly agrees. We return the bowl with no further incident but I realize on the walk back home that I forgot to suggest that my friend at least rinse out the bowl before using it again. Oops.