I tried putting my foot in the toilet, because I thought it was the stairs. I didn't even know I was in the bathroom.

Me: "WTF! Why-why is the stairs wet?"

*looks down*

Me: "...Damn."

I also put the milk in the cabinet and the cereal box in the refrigerator by accident. But, I've done that more than I care to mention. Eh, it's crazy what you do when tired.