Monsters and Piggy-tails

Tonight is Tyler's "Monster Concert" at the High School. It is called such because the entire music department is involved...it's held outside on the football field.
I was fixing Grace's hair this morning. We're still in that beautiful phase where she lets me do ponytails and piggytails and other wonderful things to her hair each morning. I know from experience that this will end in the next 12-18 months and she'll be in the world of "doing it myself!" But I digress. Here is our conversation:
me: "Remember what we're doing for family night tonight?"
her: "oh yeah...Ty's monster concert."
(at this point, she flashes those chocolate brown's at me quickly, a little furrow between them)
her: "I wonder what monster he will dress up as..."
me: "ummmm.....(how did I let this misunderstanding happen!?? Don't laugh...don't show emotion and make her feel silly!!!!????) umm...what do you think?"
her: " I think a black one with red horns."
me: "oh."
At this point she's busy brushing her teeth, so I let it drop. While we were in the car on our way to school I mentioned nonchalantly that the concert was called "Monster" because it's big. There won't be any real monsters there. I'll never know if she was relieved or disappointed.
Add this to the "You'd think we'd have figured it out by now" file. It isn't her fault that we blithely toss around phrases and situations that she has no way of deciphering!?