What's Happening!! was created by Eric Monte, who also worked on Good Times, and the series was loosely based on Monte's own film Cooley High.

It is considered television's first African-American sitcom to focus specifically on teenagers, making it a groundbreaking show for its time.

The show was Bud Yorkin's second series after ending his partnership with Norman Lear and Tandem Productions, and was produced by TOY Productions, formed by Yorkin, Saul Turteltaub and Bernie Orenstein.

The pilot episode, 'The Birthday Present', was videotaped in front of a live audience at ABC Television Studios in Los Feliz, Los Angeles, on March 16, 1976, before the show moved production to the larger Golden West Videotape Division Studios for the rest of its run.

Although 'The Runaway' was actually the second episode taped, it was chosen as the series premiere because it featured a short scene showcasing Fred Berry's dancing skills.

During the second season, Fred Berry and Ernest Thomas staged a walkout during the episode 'If I'm Elected' over pay and accommodation demands, forcing Haywood Nelson to carry the episode with Shirley Hemphill, Bryan O'Dell, and Debbi Morgan stepping into larger roles; producer Bud Yorkin responded by suspending the pair and making them sign $25,000 promissory notes to return.

Mabel King pushed producers to bring her character's ex-husband back full-time to portray a strong married Black family, but when they refused, tension on set led to her role being drastically reduced in the second season, with her character often just said to be 'at work'.

The role that became 'Little Earl' was originally intended for ten-year-old Gary Coleman at the suggestion of ABC president Fred Silverman, who believed Coleman was destined for stardom; after Silverman left ABC for NBC in 1978, he instead created Diff'rent Strokes specifically for Coleman.

In the third season, continued pay disputes led Fred Berry to skip the episode 'Dee, the Cheerleader,' and a heated confrontation where Berry accused producers of racism ultimately led to the show's cancellation.

Fred Berry was a founding member of the real-life dance group the Lockers, who appeared in the first season portrayed as a group called the Rockets that Rerun auditions for.