My gray kitty Squee (Rainbow Bridge) used to sit in my gray computer chair - but at the very back of the seat in the shadows. So even if I checked, I still couldn't tell he was there. Then I'd sit down and feel this warm wiggly thing by my butt - EEEEEK!!!

Fortunately, the shape of the chair and the shape of me let Squee fit right into the safe, if tight, space. He liked it there for some reason, but would let me know it was time to move with his claws!!!! OUCH!!!