Alan (Jon Cryer) asks Sherri (Jeri Ryan) if she had been to that restaurant with Charlie (Charlie Sheen) before. It is actually the same waiter, "Bobby" (James Edson), who served Sherri and Charlie in Bad News from the Clinic (2004). James Edson would appear as "Bobby" in a total of seven episodes.
Rather than being spoken, the episode title is a description of the sound Alan makes when telling Charlie the name of "the planet Sherri comes from", and again in Sherri's bedroom, when he sees her in her negligee.