I once had a key to a neighbouring friend's house because we shared some resource. One day I let myself in - expecting no one to be home. Inside there was a loud sound of bumping, screaming, and moaning. Oops - a quiet retreat to avoid disturbing their "I'll have what she's having" moment. NSFW
A bit like the lodger next door who was quickly labelled "Roger the Rabbit" for the wall penetrating loud noises made by his girlfriend in apparent ecstasy late at night.