Funny how things turn out. When "Family Ties" started, everyone thought that Meredith Baxter Birney was the star as opposed to Michael J. Fox; anyone who put money on Neve Campbell being a bigger name than Jennifer Love Hewitt after "Party of Five" ended would not have been considered mistaken; and similarly, when Richard Grieco joined the cast of "21 Jump Street" and drew attention away from the perpetually miserable-looking Johnny Depp, it did look like he'd be the breakout star.
So he was booted out of the force, became a private detective in his own series "Booker" (complete with Billy Idol's "Hot In The City" with the words "NEW YORK!" blanked out - due to the show taking place on the other side of the country!), and... wound up being cancelled a year before "21 Jump Street." And to be honest, you can see why; while there aren't many cop shows about people going undercover in schools (well, there was "The Mod Squad"...), there wasn't anything about the show that really made it stand out from any others of its type, and it didn't help that his assistant was played by the ever-annoying Lori Petty.
Johnny Depp went on to pull Winona Ryder and Vanessa Paradis (we'll forgive him for Kate Moss) and deliver a string of impressive performances in high-profile movies; Grieco went on to "If Looks Could Kill" (or as Joss Whedon called it, "If Looks Could Fail At The Box Office") and "A Night At The Roxbury." It's called having the last laugh.