The fish itself — the one that figures in ads for the new play “Fish in the Dark” and can be seen on the drop curtain at the Cort Theater — is pretty great, a charming and maddening creature destined to capture your heart. O.K., if you insist: It is pret-ty, pret-ty, pret-ty great.

The show for which this fish stands? Not so much.

If you don’t recognize what all those “prettys” signify, do not feel obliged to read further. (But if you do, I promise to return to the enchanting fish later.) The use of “pretty” as a repeated modifier, with a protracted first syllable and palate-tapping t’s, is a signature catch phrase of Larry David, the beloved comic television writer and actor.

And, yes, Mr. David does make pretty (if not pret-ty, pret-ty) good use of said catchphrase in the second act of “Fish in the Dark,” his Broadway debut as an actor and playwright, which opened on Thursday night. When he pulls out the prettys — as his character describes how it felt to touch a certain part of a certain woman’s anatomy — he lands the biggest laugh of the night.

It’s not the sexual content that elicits the roar. It’s the pleasure of hearing words made familiar on a hit television show, Mr. David’s “Curb Your Enthusiasm,” by the man who first spoke them. Those “prettys” are a bone with a bow tossed to an audience of expectant fans, rather in the manner of the Rolling Stones’ singing “Satisfaction” toward the end of a live concert.