I love this. It's good to see an artist still using good ol' pencil/pen and paper. Maybe the spray didn't work because the shower curtain is made of...vinyl. Vinyl is a type of plastic. Well...shut up!
Yes, there are errors here and there, alas I always end up noticing them a few days after the piece has been uploaded, and with my work being traditional, it's very hard to edit it and make the edit blend in naturally.
Also, there's another goof you've missed out. Vinyl's toothbrush seems to have disappeared!