You go in the playroom and find an interrogation chair built entirely of Legos.
You come home and find the kids tickling a bound and gagged baby-sitter.
You tell your daughter she's too old to spank, and she assures you quite firmly that she isn't.
You yell to your daughter to do her chores, she answers she's tied up right now... and she really is tied up.
The kids' favorite game is Cowboy and Dominatrix.
Your son earned his merit badge in tying knots... twelve times.
You notice your son's G.I. Joe has Barbie on a leash.
You bought a clothes dryer because every time your kids went out to play, the clothesline and clothespins vanished.
You ask your son to walk the dog, and later notice the dog's still home, but the leash and your daughter aren't.