Tetra, nicknamed The Female Puppet, is the long-lost sister of the Puppet and mother of the soul possessing FredBear. She survived considerably longer than her twin, but then came back to the Pizzeria to find her son, who was taken into the back room. She looks like a replica of the puppet, except that she has not got tearstains on her cheeks, is visibly more feminine, and has long blonde hair coming out behind her mask, which seems less cheerful.
After she found out that her brother was the Puppet Master, she worked with him to restore the dead children. After this, she told him what she knew, and gained part of his invincibility. She, to this day, still lives with him in the box, which has gained an... upgrade, shall we say?