Samuel "Screech" Powers is the nerd of the group. Screech has tagged along with Zack since they were in elementary school and is extremely loyal to him. In exchange for doing Zack's homework and being roped into Zack's various schemes, Screech receives protection from school bullies and a general boost in his confidence; but Zack's affection for Screech is evident in spite of this. Screech is very comfortable with his geekiness and even fancies himself a "ladies' man". The rest of the gang affectionately humors Screech for his eccentricities (e.g., hiding in his locker, wearing extremely loud and mismatched clothes, and obsessing over science and chess).

A recurring storyline in the series is his unrequited love for Lisa Turtle. During the series, Screech briefly has a girlfriend named Violet (Tori Spelling); it was never revealed why they broke up. Kelly also dates Screech in an episode from the first season as a token of thanks for helping her study for a science test. In several early episodes of the series, Screech has an anthropomorphized robot named Kevin, which he programs. Screech is the class valedictorian but gives that title to Jessie, as he knows how much it means to her. However, Jessie learns what Screech has done for her and returns the honor on graduation day. Screech is accepted to many colleges, although he is rejected from an all-women's school that is his number one choice. He chooses to go to the fictional Cal U. after graduation and shares a dormitory suite with Zack and Slater. Screech is also the only character to appear as a series regular in every incarnation of Saved by the Bell. He joins The New Class as an assistant to Mr. Belding.