Since I'm a huge fan of Mad Magazine and Garbage Pail Kids it would only make sense that my favorite issue of Mad would be issue #265 from Sept. 1986. Not only did Mad spoof the Garbage Pail Kids but they devoted the front and back cover to doing it.
There aren't any nice scans of the back cover online so I scanned my own copy. That is where the "Garbage Pail Adults" cards are.
Here are close-ups from the scan of the back cover:
Here's a spoof from Wacky Packages Series 5 card #28: