|Status||Dating Neil Zimmermann|
|“||Oh, great, she's in my class!||”|
|– Kat Schneider sarcastically, on Theresa|
Theresa Julia Tepper (b. 17 May 1998) is the only child of Julia and Lucas Tepper. She lives with her aunt, Irene, and Irene's husband, Babe, in Sassnitz, Mecklenburg-Vorpommern, Germany.
The Teppers are an old family, dating back to the late 13th century in the Holy Roman Empire. Theresa's mother, Julia Tepper née Beck, was Finnish, and her father, Lucas, was half-Irish.
Theresa was born on 17 May 1998 in Düsseldorf, Germany. Her father died of cancer shortly after her birth. Not much has been revealed about her house in Düsseldorf, but according to Theresa Tepper, it had air conditioning, a window on the ceiling, three televisions, and two secret passageways. When Theresa's mother died in 2009, she was taken over by her Uncle Babe and Aunt Irene. She moved to Sassnitz three years later.
Theresa moved to Sassnitz in early September 2012. She auditioned for the Hasso T. Binder School and got in. Her first day at the Binder School was 1 October. She quickly developed a crush on Neil Zimmermann III, who, to Theresa's dismay, was dating Laura Gresch at the time, so she quickly made friends with Laura's sister, Natja, and with Kat Schneider. Neil broke up with Laura in January 2013, however, and Theresa started secretly dating him, although this wasn't official until 1 July 2013.