is first introduced, Derek says he blends in with his surroundings. Derek reappears in the series finale of Fuller House when Danny and Joey try to find someone to officiate the triple wedding. Lisa Leeper Lisa Leeper (portrayed by Kathryn Zaremba) is one of Michelle's friends (featured in six episodes during the eighth season, beginning with "I've Got a Secret"); in the episode We Got the Beat," Lisa is shown to be an extremely good singer when she sings a duet of "Don't Go Breaking My Heart" with Derek. Nelson Burkhardt Nelson Burkhardt (portrayed by Jason Marsden in Full House, Hal Sparks in Fuller House) is a love interest for D.J. that is introduced in the season eight premiere "Comet's Excellent Adventure". Nelson is a teenager who comes from a very wealthy family, and dates D.J. on-and-off for some time (ironically, it is in his first appearance that D.J. breaks up with him; he ends up going on a date with Kimmy three episodes later in "I've Got a Secret"). Not much is revealed about Nelson's background or family, aside from the fact that he is very rich, and often throws and attends big parties on yachts. Though in "Taking the Plunge," he mentions that his cousin, Regina – with whom he sets Joey up on a date – is visiting the United States from England. Toward the latter stages of his "relationship" with D.J., in "D.J.'s Choice," he gets into a "tug-of-war" with Viper to be D.J.'s boyfriend, to which she declines both boys. Nelson shows up to his and D.J.'s 20th High School Reunion in season two of Fuller House. Karen Penner Karen Penner (portrayed by Debbie Gregory) is the aunt of one of Michelle's friends as well as one of Danny's girlfriends over the course of the show. She met Danny at Michelle's circus party in the season 3 episode "The Greatest Birthday on Earth", where he instantly fell for her, inviting her to stay for the party and also giving her a heart-shaped balloon. In "Lust in the Dust" Karen became Stephanie's dance teacher later in season three, and Danny started going out with her after the two kissed. They got along well until Danny found out she had trouble maintaining a clean apartment. He broke up with her because of that, but after talking it over with Jesse and Joey, he returned to her apartment