The 1997 Pontiac Astro Wagon (possibly spelled "Astrowagon") is a minivan Mr. Burns wins from the give-away competition at the Springfield Isotopes baseball game in "The Twisted World of Marge Simpson." Mr. Burns drives off in the van after angry fans start hurling pretzels at him.
The name is derived from several General Motors products - the Chevrolet Astro minivan as well as the Pontiac brand. Although the van shown is indeed a Pontiac, the Astro was made by Chevrolet and, a 1990-1996 Trans Sport minivan was shown for the representation of the "1997 Pontiac Astro Wagon." Note that for 1997, the real-life Pontiac Trans Sport underwent a major redesign, with an all-new exterior design and new interior; therefore the van in the episode could not actually be a 1997 Trans Sport.