smell what The Rock is cooking
To go into a one person bathroom after someone who took a huge crap gets out and have to smell their after-effects when you try to do your business.
Example:
Friend: I can't believe you went into that bathroom! It stinks!
You: I had no choice. I had to piss, but I really had to smell what The Rock is cooking in there.
Friend: I can't believe you went into that bathroom! It stinks!
You: I had no choice. I had to piss, but I really had to smell what The Rock is cooking in there.