Tim and Eric have a knack for taking a subject that is often perceived as immature, a subject that many people (myself included sometimes) like to think they're above (like poop jokes) and totally breaking the viewer down into fits of laughter. Oftentimes with Tim and Eric, it's not the joke or script that's necesarrily funny, it's the way they present it. Diarrhea was a great performance.
The part after the dance was hysterical.
"Thanks, Boro. Wait in the car."
It's interesting to see how the dance worked in a more intimate venue since they've been doing it at live shows on tour since at least 2009.
Oh, and the teacher was spot-on casting. Her style and taste in clothing was just like my high school Chemistry teacher's.