Danica McKellar -- Fishnets and Stilettos

Kevin Arnold would LOSE HIS MIND RIGHT NOW.

Former "Wonder Years" star Danica McKellar flaunted her figure in a punk-rock-meets-Hollywood-streetwalker outfit yesterday ... and damn, she looks GOOOD.

McKellar -- who's 38 years old BTW -- rocked the look for a new Avril Lavigne music video.

Avril was there too, but who cares.