Fans of SCR Yed will notice that Masaru is basically Kazuma in a Digimon series, both because of his personality (and tendency to punch things larger than himself) and his voice. And the all the punching. Did we mention that?
Celebrity Voice Actor: In the Japanese version, Yoshino was voiced by Yui Aragaki, a famous teen model-turned-actress-turned-singer
Agumon is "Takatomon", due to having the same English voice actor as Takato.
Hey, It's That Voice!: Both the Japanese original and English dub went out of their way to bring back actors from previous seasons. English writer/director Jeff Nimoy specifically asked fans on a message board which actors they would most like to return.
As far as actors that haven't done major Digimon roles go, Marcus is Raiden and Gaomon is Gai.
The Other Darrin: One or two cases in the English dub of the video game "Digimon World Data Squad" due to being done before the TV series. (There's also a few other differences, such as the use of "Digisoul" like the Japanese version instead of "DNA".)
Kouki's Japanese voice actor, KENN, is most often known as Judai Yuki in Yu-Gi-Oh! GX. In the same series, Agumon's seiyuu voiced Manjoume!
Sequel Gap: The series followed the 3 year gap caused by the poor performance of Digimon Frontier. Its own poor performance resulted in another 3 year gap for the franchise.
What Could Have Been: Kouki wound up as a near Complete Monster who most-likely only got away because of the fact that he never actually managed to commit mass-murder anywhere near Kurata's level. However, the original plans for him was to be Not So Different from Masuru, being very similar in many ways but unlucky enough to have been found by Kurata instead of DATS.
The original plan for the series is worldwide Delinquents tournament using Digimons, and that Yoshino and Thomas would end up being a local gang leader and an American mafia, respectively.