Was this show supposed to be a period piece?
They never really make reference to any kind of date in the show, and maybe time is irrelevant because it's supposed to be a parallel universe where humans have purple and green skin, but a lot of things about the show seem very antiquated, even for the '90s. My guess is that it depicted life in the 60's It may have been the writers writing about what what life was like when they were growing up, which could have been the 60's.
A few things (keep in mind, when I see these days, I mean 90's):
-They're favorite band was the Beats, an obvious reference to the Beatles.
-The hangout being Honkerburger seemed like a 50's/60's style thing for kids to do.
-Elementary School kids were just running around town without their parents worrying about where they were (but that was also probably for making plots more available too).
-The IQ test that they were given has been out of vougue for a long time, and seemed like a typical thing you would see in older time periods, they even physically measured Skeeter's brain.
-The school didn't look modern. It was comprised of several buildings, and the lockers used old-fashioned seperate locks. Plus, Elementary Schools don't have lockers anymore.
-The Elementary School went to 6th grade, that's rare these days.
Let me know if anybody else catches anything. And yes, I think that the ABC version was contemporary, but this is talking about the Nick version.