Are there any occurrences of TV shows airing more than one original episode on the same day? Usually, this happens with two-episode or double-length season premieres or season finales, or even series finales.

Seinfeld, Friends, The Cosby Show, Family Ties

Here's a great example:

The final season premiere of Charlie's Angels on November 30, 1980 featured a two-hour season premiere called "Angel in Hiding", followed by the regular-one hour "To See an Angel Die", all part of a special series of wraparounds, hosted by the three current leading ladies from the program called "Night with the Angels".

Just tonight CSI aired 2 new episodes on Sunday. Galavant has aired 2 back-to-back episodes for all of its 4 week run.

This is a very common practice now days. An old example: April 5, 1981, CBS aired two back to back episodes of One Day at a Time.

Parks and Recreation is airing back-to-back episodes for its final season.

The Golden Girls during season seven quite a few times.

In the '90s when NBC aired "Saved by the Bell: The New Class", from the second season through the fifth, two episodes were broadcast each Saturday morning. One episode took place in the school and the other was typically one of the "weekend job" episodes or in other words the gang outside of Bayside. I don't believe they did that with seasons 6 and 7 (which were filmed as one season but then broadcast as two).

Off the top of my head I think I've seen this done with The Simpsons, Family Guy, Modern Family.

In the '90s when NBC aired "Saved by the Bell: The New Class", from the second season through the fifth, two episodes were broadcast each Saturday morning. One episode took place in the school and the other was typically one of the "weekend job" episodes or in other words the gang outside of Bayside. I don't believe they did that with seasons 6 and 7 (which were filmed as one season but then broadcast as two).
It also happened with the first series.