C-3PO, or canonically C-3PYOLK, is the Angry Birds Star Wars I and II version of Matilda. Their canon name, "C-3PYOLK", is a pun on the word "yolk" and the name "C-3PO".
In the storyline of Star Wars, which the game is based on, C-3PO is bought by Luke, along with R2-D2. (after they escape the Dark Side troops and are kidnapped by Jawas) After this event, they do play a part in the cutscenes, but both C-3PO and R2-D2 are not playable characters in the story episodes.