Actually, Bert wrote the play about dental hygiene, which led to the funny dialogue between Bert and Prairie in the beginning. She says that if you think this play is good, "you can thank Bert", but if you think this play is awful, "you'll have no one to blame, but Bert." Bert, who's already nervous, yells at her to stop that.
Other funny dialouges were between Bert and Herry concerning "throwing himself in the skit" and of course the classic finale with Cookie pretending to throw water on Bert. Definitely one of the better ones.
The one about the caterpillar was good too, but somewhat unusual. For one thing, Prairie Dawn is not the girl at the piano. Ernie loses the picture of the cocoon, but there seems to be no reason for it in the skit, and finally, when Herry goes up in the air, he looks like the puppet he is with no feet. Sesame Street usually does better with putting feet on muppets when necessary. Still, it was also very enjoyable.