“Beach Blanket Babylon” isn’t the only manic musical event in North Beach these days. Just around the corner in the Palace Theater an immersive show is playing until November 27. “Speakeasy” is a cabaret and a casino, with 35 characters enacting a tangle of plots from the Prohibition era. You don’t just sit there, you follow them around the vast theater and its hidden passages to trace their twisted stories. Period costumes are encouraged and if you don’t have one, they’ll dress you up for an additional fee. $65-$315.