Sometimes he reads or works with his feet up on the desk right in my peripheral vision, and sometimes when we study we momentarily miss each other, so if it's me doing the missing I tickle his feet and if it's him doing the missing he gets up to squeeze my shoulders.
It didn't occur to me that this was a regular thing until I turned to stroke his arch and saw this:
It's just: Ha! It's not alarming, but if you take a moment to think about it, it's really weird. That he did this, quietly, undetected, and then put his foot up without a word. Knowing I would turn back? How could he have focused on his reading, knowing at any second I could look over and start laughing? The anticipation! He hates suspense.
The more I think about it, the more it makes me laugh.