Age: Unknown, appears to be a child
First Appearance: The Binding Of Isaac (2011)
Series Debut: SuperSpy Luigi: The Basement (2013)
Isaac appears to get frightened easily. He still will fight if he has to though. Unlike Waddle Dee, he has the guts to walk on bloodstained floors and carcasses. Isaac is able to stay alone for a long time.
Luigi: When Isaac met Luigi, he had no idea who he was, which surprised him. In SuperSpy Luigi:The Basement, they are neutral friends. Luigi seems annoyed with Isaac's cowardly behavior, while Isaac doesn't even want to be with Luigi.
Double: Isaac was also very confused about who (or what) Double was, but he knew it wasn't a friend of his. He journeyed through the Cathedral and fought Double with the help of Luigi. After that, Isaac ran off.
Music used for Isaac
Battle Theme: http://youtu.be/L55nDF9c_M0
Main Theme #2: Sacrificial
Death: In That Kid, when Double entered the School, she used her abilities to fling Isaac into the air, and ending up landing on the Schools "Welcome!" sign. But he is seen again in The Kid Strikes Back, he is seen perfectly fine (Besides being stuck inside his locker.)
- Isaac cannot use his tears to defeat enemies in Ninten World. They are much stronger in his own world. There's a gag where he tries to defeat Double with his tears, but just gets her annoyed, resulting in Isaac running away in frustration.