Memory, when conveyed on stage, traditionally arrives in the form of a flashback, or a soliloquy. But in John J. Caswell, Jr.’s frantic and surreal family drama Wet Brain, memory is a foreign object to be cut from the stomach, or a hypersonic shared experience that blasts through outer space even as it is grounded in that most triggering of locales, the family room in the house of a decidedly dysfunctional brood.