When guests come over to my house, I have little mini football helmets I keep on top of my tv. I have a Kansas City helmet, but when they go to the bathroom I switch it up with a patriots helmet. No one has noticed yet but someday one person will.
I'm also thinking about getting a painting of a waterfall, and on the back have a painting of Mona Lisa, I think that is more obvious. I also like to leave such one square of toilet paper on the roll when people come over incase they have to shit.
What are some other ideas?