Sikko Warner (pronounced SEE-ko) was introduced in Season 2 of Zany to the Max. She is the only one of the nine Warners who is adopted. It is unknown why she has an accent like Wakko's.
Sikko Warner was born somewhere in Animenia. Little is known about her biological family except that her parents died when she was very young. Soon after, she was adopted by Dakko and Samantha Warner, Pakko, Makko, and Jot's parents. In 2008, when she was 10 years old, she moved to Acme Acres, California, with her siblings, Pakko, Makko, and Jot, and their cousins, Zak and Ko. A year later, they began attending Acme Looniversity, which they graduated from in 2012, at which time they were drawn up at the Warner Bros. studio, where they, with Yakko, Wakko, and Dot, started Zany to the Max. Sikko, however, was not drawn up at that time. She was drawn up much later, but fortunately, she was drawn up just in time for Season 2 of Zany to the Max.