The tumble driers in the launderette I use have got clear doors and a Google Image search for pictures of tumble driers finds far more pictures of clear-door models than the sort that you seem to have got!
Always read the washing instructions on the labels of all household pets. ;-)
My mother had a cat that would sneak into the dishwasher if you left it open when you filled it. You had to check she wasn't still in there when you switched it on...
even though washing machines have clear doors I managed to add my reading glasses to the last wash I did. This has cost me 99 quid to have them re-lensed at specsavers. :o(
My Daughter's next door neighbour, turned the tumbler on and then went out shopping... She had a beautiful English blue cat, he was amazing. He had climbed into the dryer and she didn't know until she came back from shopping (RIP Bromley)