Shout out to Anne Sellors, her only role ever was in the movie Threads and she was credited as ‘Woman Who Urinates on Herself’ (though technically uncredited.)

https://www.imdb.com/name/nm1856457/

Here’s the scene, it’s actually terrifying. (Anne seen at 1.15)

https://youtu.be/MrHoMSRZOS4