Ruby Bird is a girl from Greg's school who appeared in The Third Wheel. She is the only girl to have ever been suspended, for biting Mr. Underwood's arm so hard that her front tooth is lodged in it. Fregley has a huge crush on her. When Ruby Bird and Fregley got paired up, they were acting affectionate, but according to Greg's Relationship Chart, she bit Fregley.
At the dance, when it was about to end, Ruby didn't had a partner so she was walking towards Greg to get him to dance with her, but she didn't because just then Greg grabbed Abigail's hand and went to the floor with Abigail instead.
- Ruby Bird behaves much like Fregley, she has a habit of biting people, she also has only one front tooth as one got lodged into Mr. Underwood's arm. She had gotten suspended for that. She also bit Fregley according to Greg's Relationship Chart, but they act like a couple when they got paired.
- Ruby is a very skinny girl, she has black pigtails and has a tall oval face and wears glasses. She also has only one front tooth because of her habit of biting people.
- She and Fregley are the only characters where both of their ears are always shown. This also applies to the two overweight Beardo Kids.
- It is shown that she has bit Fregley on page 116 on The Third Wheel when Greg makes a list of who is in a relationship or not.
- Fregley may have made Ruby mad as she bit him. This may have been during the ballroom dance unit.
- She is the only "strange" or "disgusting" female student in the Diary of a Wimpy Kid series.
- Diary of a Wimpy Kid: The Third Wheel (First and only appearance)