Characters in the game exist in either of the two worlds of Big Bang Comics (the Silver Age Earth-A or Golden Age Earth-B). Players may create new heroes or take the part of existing heroes from Big Bang Comics. Characters are created with two character classes: a power origin Entry Class, and a "civilian identity" representing their out-of-costume occupation. The power origin classes include choices such as Mutant, Elite (super-trained normal), Sorceror, and Mechanical.
The game rules use standard D20 skills with a large range of original "Feats", which in Big Bang include super powers and other abilities.