Highlights from the Thirteenth Episode of Season 5 of The Big Bang Theory

Everything might change when Leonard offers Penny (Kaley Cuoco) a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon (Jim Parsons) ponders how everything might change when Leonard offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

The guys (left to right: Jim Parsons, Kunal Nayyar, Simon Helberg) ponder how everything might change when Leonard offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

The guys (left to right: Jim Parsons, Kunal Nayyar, Simon Helberg) ponder how everything might change when Leonard offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Bernadette (Melissa Rauch, left) and Amy (Mayim Bialik, right) ponder how everything might change when Leonard offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Everything might change when Leonard (Johnny Galecki, left) offers Penny (Kaley Cuoco, right) a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

The guys (Jim Parsons, second from left; Kunal Nayyar, second from right; Simon Helberg, far right) ponder how everything might change when Leonard (Johnny Galecki, far left) offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon (Jim Parsons, right) ponders how everything might change when Leonard (Johnny Galecki, left) offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved. Winning caption by: Joshua L.

The girls (Mayim Bialik, second from left; Melissa Rauch, second from right) ponder how everything might change when Leonard (Johnny Galecki, far right) offers Penny (Kaley Cuoco, far left) a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon (Jim Parsons, right) ponders how everything might change when Leonard (Johnny Galecki, left) offers Penny a spur of the moment invitation to a romantic dinner for two, on the 100th episode of THE BIG BANG THEORY. Photo: Robert Voets/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.