Tessie is one of the official mascots of the Boston Red Sox, making her debut in the 2016 season. Tessie is Wally the Green Monster's little sister. She was introduced to the public in January 2016. She was named after the the song "Tessie", a long time anthem of the Red Sox. Since 2004, the song has been performed by Boston natives The Dropkick Murphys, who updated an original turn-of-the-century broadway tune into a modernized classic, complete with Red Sox-centric lyrics.