Factual error: At the start of every episode we see the gang driving. Cars in the background are not from the 70s but the late 90s. For instance, the truck that comes up beside them at the end is a 90s Ford F150.
Factual error: Eric has diecast model cars in his bedroom; those were not around then. The ones he has weren't available until the 1990s.
Answer: It's Ashton Kutcher's dog.