What does it mean to be a show's "screech"?
The Drop the Mic battle between Kunal Nayyar and Mayim Bialik has the following line from Mayim Bialik:
You're basically our show's Screech.
The battle between Ashton Kutcher and Sean Combs has a similar line referring to Screech, so this seems to be a somewhat common reference.
I don't get it though. Looking online, it seems that it might be a reference to Samuel Powers from Saved by the Bell. Is this correct? What is the nature of the Samuel Powers' character that would explain the line?
Screech, as you pointed out, was a comic relief but somewhat annoying character from Saved By The Bell (1989-92). He was played by Dustin Diamond, an actor with a troubled history who would eventually be arrested for possession of a switchblade knife after stabbing someone in a bar. His career never really went anywhere, much like his character on Saved By The Bell.
As such, a "Screech" is someone who is basically an annoying loser.