Back to the topic!
It was established way back in
The Making of Star Trek that GR tried to keep things light as possible within the constraints of the pressure making the show. The small practical jokes like putting a fully made up Ted Cassidy -as - Ruk in Gene's office to meet an unsuspecting salesman, the small after work parties (which was a Desilu tradition anyways), the memos with the sarcastic edge to them. It's all part of relieving the pressure a little.
Favorite Justman memo of all:
TO: All Concerned
FROM: R Justman
SUBJECT: TUESDAY
I plan on being extremely mean today.
There's a reason the Trek bloopers are some of the best of all time....