Sealab 2020 (lost unaired episodes of NBC animated series; 1972)
Sealab 2020 was a animated series that aired on NBC at 11 o'clock on Saturday mornings. The series ran from September 9, 1972 to December 2, 1972. There is 15 total episodes with the last two being unaired. The two unaired episodes were "S.O.S.: Sealab Ocean Signal" and "Utopia of Cassidy". The episode "S.O.S.: Sealab Ocean Signal" is about the crew being in danger from a possible from chemicals and the episode "Utopia of Cassidy" is about the crew finding a supposed island of paradise. There is not much more known about these episodes, including why they were not aired even though they were already made.
There was a reboot of the show on Adult Swim called Sealab 2021 that used stock footage from Sealab 2020 and could possibly have animation from these episodes.