Anachronism I haven't seen mentioned....

While I _have_ seen people mention Krispy Kreme (they didn't have a store in Wisconsin until 2000 or so, but the donuts were in at least a few episodes)...

I haven't seen this one mentioned. In the episode where they're touring colleges and Donna goes to Marquette, there's posters up for the "Golden Eagles". From the mid 1950s to mid 1990s, Marquette was the "Warriors". The "Golden Eagles" name didn't come about until 1994.