Once I was waiting for second class, since I had arrived too late for the first, and I noticed a new person sitting next to me on the bench. Whatever got into my head to say the following, but now I know after reading Linda's explanation! I said to the spectator,"Don't worry, it's all done with mirrors"
I used to work in the same building as my first dojo. Finished work, went to watch the last half of a class on the way out the door. Elderly gentleman sitting on the bench, watching. I asked a few questions, including if he'd seen Aikido before (I wasn't gokyu yet.)...
He said he'd seen a little.
Next day's class, I turn up and there he is at the head of the dojo in a hakama et al., Guest Instructor...
He'd seen a little - only about 32 years worth...