Billy the Sign is a Mechanical Bird who serves as the mascot for Matilda's Anger Mangagement Class.
Voice Actor: Catherine Winder
Billy was outside Matilda's Anger management class when Red was going there after being sentenced there, as Billy was rocking back and forth, Red was starting to get angry, even clenching his fist at him! Red, instead tries to walk inside but Billy hits him back and after a few seconds, Red grabbed him and attacked him. After Red attacked Billy, he brought Billy back up right and and as Red is walking in, one of his tooth falls out
Later, When Chuck presented his presentation to the class after Bomb's poem, and called it a "hate crime", showing Billy's corpse and reveals that Chuck was the one who created him and even showed to everyone who did this: Red. It angered everyone and Terence even punched him into a wall as punishment. Soon the birds joined together to remence of Billy's death, and Red wanted to join in but Terence refused to let him in because he destroyed him. When Matilda, Chuck, Bomb, and Terence hears something outside they go outside crushing Billy in the process.
Later on in the film Billy was seen on the Piggy Ship when they are about to leave Bird Island.
Billy (named Piñata) appears in Angry Birds Pop 2 as the device containing to get power-ups. characters, cards, and gems.