SE has always loved to sit, lean against or lie down on people. When she was tiny, she'd lie down on people's lap until it wasn't possible to go anywhere. Now when we watch TV, she'd use someone (usually me, sometimes hubby) as a human chair. She'd get up to take something, and return to plonk her backside where it was. If I push her off to go to the loo, she'd make herself comfy again when I'm back.
Shouldn't complain, it's rather nice having a child snuggled against me like that!