This was supposed to be the 3rd season finale, but was delayed until the 4th season due to the 2020 COVID-19 pandemic.
The scene of Missy's graduating class singing was shot in a re-purposed church.
Despite his future The Big Bang Theory (2007) near-catatonic fear of public speaking, Sheldon manages to give his valedictorian address.
Sheldon graduates with the high school class of 1991. In real life, Lance Barber (George Cooper, Sr) graduated high school the same year.
Mayim Bialik: Sheldon's future wife, Amy Farrah Fowler, from The Big Bang Theory (2007) (voice only).