The order of the episodes. The three episodes featured in Tarzan & Jane apparently were produced later than the rest (since the show itself aired in 2001, while the direct-to-video film was released in 2002). However, at least two of those three episodes, namely "The Volcanic Diamond Mine" and "The British Invasion", obviously take place before two episodes of the show, "The Caged Fury" and "The New Wave", respectively, since the events of the former two are referenced in the latter two.
In the episode where Terk asks Jane to teach her to be a "proper lady" to impress a male gorilla, why on Earth did she think a gorilla would be interested in human behavior? Much less victorian-era British ones?
Jane and Terk briefly grab the Idiot Ball for the joke's sake. It's the reversal of the joke from George of the Jungle where George wants to impress Ursula and asks advice from Ape, who teaches him gorilla courtship behavior.