Vaseline. Oh yes, the time I went out to play in a darts match. Leaving behind DP, looking after DD (aged 5ish) and DS (aged no more than 18 months).
DS was put to bed. Turns out he can climb out his cot. He grabs the Biiiiiig jar of Vaseline. And smears everything. Walls, cot, bedding carpet, himself. And did it silently so DP only realised what he'd done when he went up to check him.
I came home to find that DP had sorted DS out, clean bedding, clean clothing, etc, and after putting him back to bed, was downstairs having a (very quiet) rant, pacing about the kitchen.
We did manage to clean the furniture and walls over the next day or two, but it wasn't until someone told us to iron the carpet with newspaper between carpet and iron that we got most of the stuff out the carpet.
Oh well, we can laugh about it now. 