Well, all right–“under sheets.” Doesn’t have the same ring to it, though, does it?
Our cat Buster loved messing around under the bedding. He and Missy dug their way into the bottom of the mattress. I can’t forget the two little heads sticking out… upside-down.
That is what cats and kittens do. I had the two Siamese who did this all the time.
Blankets, sheets, etc. seem to really fascinate cats. A car can see you put your hand under a blanket, but they will attack as soon as your hand is concealed. Pull the hand back out and they ignore it, but if you reach back under the blanket, they will attack again. They have to know what they are doing, but they like to play.
Every night, as soon as I retire, my cat wants me to lift the blankets, so she can take her nightly tour of the bedding. Then she crawls out from under and curls up on my shoulder.