Rugrats Pre-School Daze (a.k.a. Angelica and Suzie's Preschool Daze) is a very short-lived spin-off of Rugrats, which focused on Angelica and Suzie as they entered preschool. It was adapted from the Rugrats episode "Preschool Daze", which served as a sort of Backdoor Pilot for this series.
If you've never heard of this series, don't worry, neither have even most hardcore Rugrats fans. Only four episodes of this show were ever produced and released; even today, it's still the shortest-running Nicktoon, and the shortest-running Nickelodeon series period. The show is quite obscure for something based off of one of Nickelodeon's most iconic franchises, and there is a very good reason for that: the series only ever saw an official release as "bonus features" on the Tales from the Crib direct-to-DVD series, and when Nick finally aired Preschool Daze between November and December 2008, it was buried in an early morning timeslot where no kid would be awake to see it.