Actually, since arsenic is a heavy metal (which you can't become immune to, which I believe is the joke), it can build up within you, so John might've already been heading towards the grave and wouldn't even have to drink that last cup.
haha, thank you! I originally did no faces because I drew the comics so small I couldn't fit them on, now I like them faceless too. I'm glad it didn't put you off, I've been told it makes them look a bit creepy. -_-'