A short one:
My wife was fostering a cat named Lucky. She went to pick him up at the vet’s after his operation and said to the medical staff and receptionist, “I’m here to get Lucky,” without realizing how that sounded until everyone burst into laughter.
A long one:
A few years ago, we shared a bungalow with my mother in law living in the built-in suite downstairs. A security system came with the house, which we never used because we didn’t want to pay the subscription fees, but was nonetheless still wired in, so every door opening made the central control box go “dee dee dee!”. We got used to it and forgot it was there.
One night about 2:00 AM, the control box was beeping regularly and continuously, “Beeeeep. Beeeep. Beeeep.” and wouldn’t stop. Frustrated and angry with it, I got out of bed, stomped down to the foyer where the control box was. My wife followed and my mother in law looked up from the bottom of the stairs, because the noise had woken everyone in the house up, and watched as I pulled off the panel and ripped out the wires connecting it to the house. The noise stopped and we breathed a sigh of relief and all went back to bed.
Lying in bed with my wife after the incident, I only then remembered I had been sleeping bottomless, so I was completely exposed to my mother in law from the waist down, who had a clear view of my dangling unmentionables from her point of view at the bottom of the stairs. My wife laughed so hard she had to pee.
The next day I apologized to her mom who waved it away, “It’s not like I haven’t seen that sort of thing before,” and we never spoke of it again. To this day, no matter how hot it gets in the summer, I always wear briefs to sleep. 
Footnote to this story is that we discovered one of the basement windows had been removed in the night and was leaning against the tree in the front yard. Someone HAD tried to break in to our house and the security system was actually only doing the job it was intended for in the first place, and I murdered it. We replaced all the windows with security lock windows after that. 