The eight kids have the same personalities throughout the series: PHOEBE: kind hearted, ARNOLD: over thinker, WANDA: adventurer, KEESHA: observer, TIM: artist, CARLOS: comedien, DOROTHY ANN: bookworm, RALPHIE: athlete
The episode Kicks Up A Storm shows the final appearance of the female producer as she wasn't a popular character.
Danny Tamberelli (Arnold) provided the voice of Ralphie for two lines in the episode Makes A Stink. Also, in the episode Getting Energized, Phoebe's voice can be heard on Dorothy Ann when falling into the river.
The child actors who voiced the students were recorded in Toronto, whereas Lily Tomlin and Malcom-Jamal Warner were both recorded in Los Angeles and New York, so the kids never got to meet them.
Arnold is Jewish. To be specific, he's Ashkenazi given the origins of his surname, Perlstein.