CBS has announced the details of the twentieth episode of the season, "The Spaghetti Catalyst", which will air May 3rd.
"The Spaghetti Catalyst" - When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy, on THE BIG BANG THEORY, Monday, May 3 (9:31-10:00 PM, ET/PT) on the CBS Television Network.
You can find more information about the episode in our Episode Guide. The scheduling of this episode means there will be only one original episode in April, but four will air in May. The upcoming reruns are: April 5 - The Vengeance Formulation, April 19 - The Gorilla Experiment, April 26 - The Maternal Congruence. Wil Wheaton returns as Sheldon's nemesis in an original episode on April 12.