Guests showed up with their t-shirts inside out, or backwards, or some other silly, mismatched ensemble.
We ate under the table, instead of at it. We served our cupcakes upside down.
They watched a silly movie and then had a sleepover, and for extra confusion, answered all questions in reverse. ("Do you want another slice of pizza," I would ask. "No, no thank you!")
The next morning, we killed a pinata, and then roamed around the bike park. The party was a hit, we had a great time.
And now our littlest gal is now in her second decade!