The trivia item below may give away important plot points.
The beagle adopted from their neighbors, The Sacksky's makes an appearance, on the couch, with Doug & Carrie, at the beginning of the episode. Apparently now living with them. Eventually, in future episodes, the pet beagle is completely written out of the series. And, point in fact, adopting a pet, to attain popularity in their neighborhood, becomes the theme of an even future episode.