Blue diamond is a secondary antagonist. She is voiced by Lisa Hannigan and has an Irish accent.
Characteristics: tall, slender, blue skin, blue hair, blue eyes, curvy, beautiful, quiet, sensitive, emotional, diplomatic, pragmatic, vengeful
Real age: 2 real years
Family: Yellow diamond (sister); the Iron giant (boyfriend)
comes from: Steven Universe
nicknames: Her sister calls her "Blue" for short.
subrace: negative character
- Yellow diamond: Blue diamond has a complicated relationship with her adoptive sister. While they both care about each other, their different points of view can often cause them to start arguing and disagreeing.
- the Iron giant: She first met him in the episode The brave robot will take the diamond. After spending time with him and seeing how kind and polite he is, she quickly falls in love with him. Step by step, she starts to see him as her new chance in life and the reason she wants to change herself. Unfortunately, she does not have the opportunity to see him often, as their relationship is considered forbidden in cartoon society (the law that a negative and a positive character must not start a romantic relationship with each other).
- Due to being voiced by a singer, Blue diamond herself has some impressive singing skills.
- Most of the time, with the help of her powers, she is much smaller than a diamond is supposed to be, but still taller than most humans. When she is in her true height, she is as tall as a titan.
- When she is crying, her powers can cause other toons start crying as well.