No plumbing yet but i did mount a TV bracket right through a pocket door. House was being renovated. Bedroom had an attached bath with a pocket door. There was also an unattached door leaning against the wall. I must have subconsciously assumed that this door was for the bathroom. A few bolts later and i am done...until the client calls me and asks why the pocket door wont slide out.

I used spray foam to fill the hole (hollow door) and bondo to finish it. Luckily the place had just been painted so i had matching paint.