Original Star Trek (1966-69)- Big hit. The network executives feared it was too much for 1960s audiences. They rejected the original Pilot in 1964 as too intellectual.
Funny enough, in the original broadcast, TOS was considered a notable commercial failure, cancelled short, budget cuts continuously, it didn't really gather any kind of popular culture mindset till years later in syndication.
Animated series (1973-74)- There was an animated series?
I'll accept your resignation as an official STN* ...
It was terrific too - well, the design was great, the animation, I guess I'd describe as "barely"
Most of the original voice cast, some outstanding writers, DC Fontana, David Gerrold, and possibly my favorite episode of TAS,
The Slaver Weapon, written by Larry Niven (adapted from his own short story). The latter introduced the Kzinti, from Niven's, Known Space novels, great stuff! It would've been cool to use them in later series, but ST:TAS was more or less "decanonized" by Roddenberry.
*Star Trek Nerd