"Kermit's Between Lecture" is a sketch that was created for and originally aired during Sesame Street episode 0070 (during the first season), on February 13, 1970.
The sketch involved Kermit demonstrating "between" by using a ping-pong ball, donut, and a Beatles record stacked on a table to show how one object was between two others. Beautiful Day Monster then comes along and eats the three objects on the table. Kermit then ducks underneath the table for cover and trembles in fear, but Beautiful Day Monster also eats pieces of the table and takes it to bits. After there was nothing left for him to eat, Beautiful Day Monster was about to eat Kermit too, but he instead gives Kermit a kiss, thanking him for letting him eat table and the three objects.
There are no copies of the sketch available online, although there is only one screenshot of the sketch on Muppet Wiki. It also cannot be found in any episodes of international Sesame Street co-productions on YouTube (i.e. Sesamstraße, Sesamstraat, Iftah Ya Simsim, Rechov Sumsum, Rua Sesamo, etc.).
It was also mentioned by a user on one MuppetCentral forum thread. This forum thread is pretty old, dating back to September of 2005.
UPDATE 7/24/18: MuppetDude confirms on a Muppet Wiki thread that he has a digital file of the Between clip (the one w/BDM and the table of objects) from Season 1, but has no idea how to upload it to YouTube, plus he is busy with other things. He confirms that the screenshot above came from the German Sesamstraße dub (hence the only international Sesame Street co-production this clip is confirmed to have appeared in, outside of the American Sesame Street).
UPDATE 2/26/19: MuppetDude finally uploads a copy of the German dub on his YouTube channel. Also, it's his first upload on his YouTube channel.
UPDATE 2/11/21: Star Dragon Dust finally uploads the English version on his YouTube channel.
- muppet.wikia.com page on Sesame Street episode 0070. Retrieved 26 Dec '16.
- muppetcentral.com forum thread on the sketch. Retrieved 26 Dec '16.