You know, Herbert may
appear to be a straight man, but if you actually watch him closely, he comes across to me more like a cheerfully friendly sadist.
He doesn't bat an eye when his lectures cause somebody excruciating pain ("Over and Under" with Grover), or keep somebody waiting for ages ("The ET Family" with that UPS guy).
(Dig this exchange:
UPS guy: "Aw come on, fella! Charlie's in the truck there watchin' me! He's laughin' his head off!"
Herbert [cheerfully]: "Well, that doesn't matter!")
He strikes me as the type who pretends to be obliviously goal-oriented, but secretly enjoys driving people nuts.
Thus, it's not hard for me to picture a sketch where he and Kermit would be co-lecturing, but Kermit would somehow be made the unwitting goat, and end up flipping out at the the way our green friend is famous for doing.