My partner and I were living at his mom's house for a while before we left the U.S. a few years ago. His adult sister lives there, too.
His sister was at work and his mom was out with friends, so we thought we had a few hours. We started doggy-style in the living room, then moved to the dining room table, and finally ended up an hour and a half later on the floor of his bedroom, after making extensive use of several different toys. We had enjoyed ourselves thoroughly, and were preparing for a little post-coital nap when we heard his sister's car in the driveway. We thought we were okay, since we hadn't left any evidence in the rest of the house and the door was closed.
V's sister comes to the bedroom door and knocks. We're all adults, and she's pretty mellow, so we cover up our nakedness with the comforter and say, "Ok, come in." She opens the door, gives an unreasonably shocked look, and starts stammering about how she came home sick from work. V and I try to have a semi-normal conversation with her, but she obviously wants to jet it out of there, so she shuts the door and leaves. We're wondering why she's so shocked, since it's not the first time she's come across us in post-lovemaking undress.
Then...I look up at the top of the dresser right behind our heads, and I realize that I have my silicone dildo suctioned to the top, standing straight up! Right next to it is the KY jelly and the leather cock ring. It's pretty difficult to maintain a normal conversation when there's an unexpected dildo staring at you.