Memorial Day is more than six weeks away, but it’s never too early to secure tickets for some summer shows and programs. Witness the return of the comedian Paula Poundstone to Bay Street Theater in Sag Harbor on May 25. As of press time, only a handful of seats remain for what is certain to be a sold-out performance.Bay Street has announced two comic additions to its summer lineup: Robert Klein on June 22 and Colin Quinn on July 27. Tickets for both shows became available last week, and since both are perennial summer hits, savvy standup fans will waste no time before visiting baystreet.org or the theater’s box office.Ms. Poundstone will bring an all-new show to Bay Street this year. Known for her sharp observational humor and her ability to improvise with the audience, she was the first woman to perform standup at the White House Correspondents’ Dinner. One of Comedy Central’s 100 Best Standup Comics of All Time, she has starred in her own series on HBO and ABC and is a regular panelist on NPR’s weekly comedy news quiz, “Wait, Wait . . . Don’t Tell Me!”Also on sale as of Tuesday are tickets to Bay Street’s first summer theatrical production, “The Prompter,” a new comedy by Wade Dooley that will open its world premiere engagement on May 28. Bay Street has just announced that the multiple award-winning actress Tovah Feldshuh will star as Irene Young, a veteran actress who is returning to Broadway after a 40-year absence. Mr. Dooley will play the young actor who has to feed the actress her lines.