I've had heaps of those moments. XD + ^^; They're usually door-related.
"Serenity, what are you doing outside? The toilet's that way."
*realises that she IS heading towards a toilet, but not the one I told her to use*
"But why would you want to use the one at the park when you have three perfectly good ones at home? Like that one..."
"...which doesn't have a door."
*laughs for five minutes before finally adding a door*
"How did I forget that? Never mind. Now to find out why Joey's sleeping outside when he has a completely accessible bedroom..."
(In case you're wondering, that didn't have a door either.)