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

Sheldon's (Jim Parsons, right) selfish demands force Leonard (Johnny Galecki, left) to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. NASA astronaut Mike Massimino guest stars as himself. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's selfish demands force Leonard (Johnny Galecki, left) to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Also pictured: Kaley Cuoco, right. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Pictured (clockwise from left): Johnny Galecki, Kunal Nayyar, Simon Helberg, Jim Parsons. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Pictured (clockwise from left): Kunal Nayyar, Simon Helberg, Melissa Rauch, Mayim Bialik, Johnny Galecki, Kaley Cuoco. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons, right) selfish demands force Leonard (Johnny Galecki, center) to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Also pictured: Kaley Cuoco, left. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons) selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons, right) selfish demands force Leonard (Johnny Galecki, left) to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons, left) selfish demands force Leonard (Johnny Galecki, right) to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Koothrappali (Kunal Nayyar, left) helps Wolowitz (Simon Helberg, right) pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons, right) selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons) selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.

Sheldon's (Jim Parsons, left) selfish demands force Leonard (Johnny Galecki, right) to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname, on THE BIG BANG THEORY. Photo: Michael Yarish/Warner Bros. ©2012 Warner Bros. Television. All Rights Reserved.