Executive Meddling: The changing of "The Geek" into a girl, from the fairly standard male nerd design he had in the Series Bible, because the executives wanted a major female cast member. In fact, the executives suggested turning Max into a girl. In regard to the firearms, however, it worked out better; in lieu of handguns, the two used bazookas, flamethrowers, and tanks at the drop of a hat. Word of God was that this was a change for the better.
Probably it's no surprise to hear Tales of Monkey Island voice actors in the Telltale Games Series and vice-versa, but, Majus, the voice of Guybrush in the I wonder what will happen in Tales of Monkey Island series of Flash Videos, animated by himself, voices an in game character in "They Stole Max's Brain!", who happens to be an European Tourist.
Andrew Chaikin (A.K.A. Kid Beyond), the first person to give Penny Arcade's Tycho Brahe a voice, voiced Max in episode 101 (he was later replaced by William Kasten due to health problems), and later returned in Season 3 as the voice of Superego (the narrator), Papierwaite, and one of the molemen.
The Other Darrin: Andrew Chaikin plays Max in Episode 101, but (apparently due to health reasons) was replaced by William Kasten. As of Season 3, Chaikin is back, but instead of playing Max, he plays The Narrator. Which is kind of playing Max anyway — the Narrator is actually Max's long-dormant superego.