What makes this episode "solid" isn't just the mystery; it’s the execution of every joke along the way:

In a desperate attempt to prove his innocence, Eric identifies the owner of the panties in the most awkward way possible—by accurately describing Donna's actual underwear.

This episode was reportedly one of Topher Grace’s (Eric Forman) personal favorites to film.

The premise is classic '70s Show : Donna finds a pair of panties in the backseat of Eric’s Vista Cruiser. Naturally, the basement crew immediately jumps to the most scandalous conclusions. Donna’s faith in Eric is shaken—thanks in no small part to Jackie’s "helpful" advice and the blundering behavior of her own parents, Bob and Midge. Why It Works