Dawson Casting: In the episode with the isolation environment. Wound up making the "long distance relationship" going on there really creepy. Completely averted by Zoe, however (Jordan Hinson is actually about two months younger than her character).
Actually it was initially inverted. During the pilot Hinson was 13 playing 15, by the time of the series she was closer to her character's age.
Fake Nationality: Canadian/American Matt Frewer as an Australian. Conversely, James Callis and Chris Gauthier are English; Colin Ferguson, Erica Cerra, Niall Matter and Neil Grayston are all Canadian. They all play American characters.
Real-Life Relative: The actor who plays Allison's brother Marcus is Dondre Whitfield, husband of Salli Richardson-Whitfield. Makes this bit of dialogue sort of meta-Heartwarming.
Allison: Jack Carter might not have the highest IQ in town, but he's the smartest man I know.
Marcus: He married you, didn't he?
Deputy Andy is one big Toy StoryShout-Out. One of Woody's pullstring phrases is "You're my favorite deputy!", something his owner Andy would have heard quite often, no doubt. And Eureka's Andy is a highly advanced android, something Woody's other favorite deputy, Buzz, would be quite familiar with.