when does callie appear in grey's anatomy
In season 2
Callie Torres
Calliope Iphegenia Torres, M.D. is a fictional character from the medical drama television series "Grey's Anatomy", which airs on the ABC in the United States. The character was created by series' producer Shonda Rhimes, and is portrayed by Sara Ramirez. She was introduced in season 2, as a senior orthopedic resident, as a love-interest for intern George O'Malley (T. R. Knight). Eventually becoming an attending orthopedic surgeon, the character was originally contracted to appear on a recurring basis, but received star-billing in season 3.

wiki:2720647
Callie Torres [SEP] Introduction
Further storylines include relationships between her and plastic surgeon, Mark Sloan (Eric Dane), cardiothoracic surgeon Erica Hahn (Brooke Smith), as well as a marriage to pediatric surgeon Arizona Robbins (Jessica Capshaw). The character's bisexual storyline with Hahn and Robbins, and her development later in the series has garnered high critical acclaim. She is also the longest-running LGBT character in television history, appearing in 11 seasons and 239 episodes. Ramirez's portrayal of Torres has been widely praised by television critics and the character gained significant popularity as the series progressed. Ramirez was nominated for several awards for her portrayal of Torres, including the Image Award for Outstanding Supporting Actress in a Drama Series, and the ALMA Award for Outstanding Actress in a Drama Television Series.