Slang for a VW bus (the Volkswagen Type 2, AKA Transporter).
Named for their uncanny resemblance to the cream-filled sponge cake... in shape at least. In the Slug-Bug game, Bugs are worth one slug, Twinkies are worth two, and VW Things are worth four, only because they are so rare. If you see a yellow VW bus driving down the street, you may mistake it for a giant rolling Twinkie.
Billy: Twinkie! (slugs Jim twice)
Jim: Aw man, you suck!
Sue: I bought a Twinkie last night, only had 220,000 miles.