It was designed as a tween version of Saturday Night Live, and, like SNL, has served as a launching pad for a number of current talents.
All That! was originally part of Nickelodeon's Snick Saturday night block when it launched in 1994. Of course, when the series took off and became a big hit, Nick began airing reruns in the Saturday AM block. Nothing new there, but suffice to say, it got more attention from ye scribe airing in the daytime.
All That!'s very recognizable theme song is performed by the R & B trio, TLC, with lead vocal by Lisa "Left Eye" Lopes. Its distinguished alumni include current SNL star Kenan Thompson, Amanda Bynes, Gabriel Iglesias, Lori Beth Denberg (later of The Steve Harvey Show), Nick Cannon (America's Got Talent), & Jamie Lynn Spears. Of this group, Thompson, Bynes, Cannon, & Spears were all spun off into other series on Nick or its sister networks within the MTV Networks family. That particularly applies to Cannon, who, in addition to being presently married to singer Mariah Carey, is also a NYC radio DJ these days, keeping busy in between seasons of Talent, and was hosting at least a couple of series on MTV before moving to NBC. Bynes famously announced her "retirement" from show business after her CW sitcom, What I Like About You, was cancelled.
The series' pedigree can be traced back to an 80's sitcom, Head of the Class. Co-stars Brian Robbins & Dan Schneider were among the show's producers, and a 3rd Class alumnus, Dan Frischman, would begin appearing on Kenan & Kel, the first spin-off series produced, particularly in the "Good Burger" skits that carried over from That!. I cannot recall whether or not he'd appeared on All That! prior to that point.
Following is a fan-made video that collects most of the cast members over the course of the series' 10 year run. Bear in mind that it actually encompasses 11 years, as there was a 1 year hiatus from 2001-02.
It's just too bad that Nick decided to end the series, when it has served as a proving ground for young talent. Then again, once early fan favorites like Thompson, Denberg, & Bynes began leaving, the wellspring was running dry, and Nick resorted to turning the series into more of a blatant SNL clone, with weekly guest stars in order to boost sagging ratings. Reruns have resurfaced on TeenNick as part of a late night block dedicated to classic Nick programming from the 90's.