Sparky is a Jack Russell Terrier, who is owned by Teddy and his family. He is only in a few episodes. It's hinted that Sparky goes with Teddy's family when they move to Texas. Sparky later returns when Teddy's family moves back home to San Francisco.
In the episode "The Volunteer," he is given four out of five stars in the Tanners' dog show, which he won for his "funny walk". He also appears in the episode "One Last Kiss." He attends Comet's birthday party, and Michelle wants to keep him because Comet has grown too big for her (through the use of her hands: close together for small, far and wide for big). To hide him from the rest of the family, she puts bunny ears on him, and calls him "Peanut". Apparently, D.J. finds him and takes him home, but not before explaining to Michelle that pets growing also applies to humans growing: It takes time; however, pets grow faster than humans. She goes on to explain that Comet may have stopped growing, but as soon as Michelle stops growing, it'll look like he's getting smaller and she's getting bigger, though in reality he's (roughly) the exact same size as her.