James Ijames has borrowed rudiments of Shakespeare’s Hamlet to jump-start his roistering new comedy Fat Ham. A coproduction of the Public Theater and the National Black Theatre, Fat Ham is a dramaturgical ragbag, blending bits of the greatest tragedy in the English language with Southern Gothic caricature and sitcom tropes from Tyler Perry and the chitlin circuit. Saheem Ali has directed the show’s endearing cast with verve and velocity comparable to his lightning-paced Merry Wives in Central Park last summer.