One of my teen sims had a wish to buy a basketball hoop. She then shot around till stinky. When she was showering she autonomously queued up the action to "Dream Big" and then this happened! I think she actually made the shot in the shower but I didn't catch the image.
She finished her shower and then went to bed. I had a few other sims in the household "shoot around" and then take showers and no one else had the "Dream Big" action in the shower.
No third party.
Comments
It may be related to the issue in this thread on the AHQ EA site
http://answers.ea.com/t5/The-Sims-4-Bug-Reports/OPEN-Underwater-Flip-Animation-outside-water/m-p/5681820#M29727
The animation occurs when there is a basketball hoop on the lot.
Your issue is a little different though.
http://forums.thesims.com/en_US/discussion/817478/hello-come-and-introduce-yourself
http://tinyurl.com/OneRoomOneWeek
http://tinyurl.com/rosemow
My Showcase thread https://forums.thesims.com/en_US/discussion/948861/rosemow-s-rooms-showcase
Mini Micro Builds Challenge
Sprucer Upper Challenge: A Play to Build Challenge
The Sims Creators' Consortium
http://forums.thesims.com/en_US/discussion/817478/hello-come-and-introduce-yourself
http://tinyurl.com/OneRoomOneWeek
http://tinyurl.com/rosemow
My Showcase thread https://forums.thesims.com/en_US/discussion/948861/rosemow-s-rooms-showcase