Karen Penner is the aunt of one of Michelle's friends, and one of Danny Tanner's girlfriends over the course of the show. She appears in two episodes of season three and is portrayed by Debbie Gregory.
She met Danny Tanner at Michelle's circus party, where Danny instantly fell for her, inviting her to stay for the party and also giving her a heart-shaped balloon.
Karen became Stephanie's dance teacher later in season three, and Danny started going out with her. 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 with Jesse and Joey, he returned to her apartment to find that she had cleaned it (by shoving everything in the closet) and he apologized. They continued their relationship until sometime in either season three or early season four. It is unknown when or how they broke up.