tbbt the big bang theory cast

This TBBT friendship is one that nobody can understeands. Is the Raj ans Howard´s friendship. We know that they have lost of things in common, like the sociological clichés and the geeky parts in their personalities. Also we know they have especial problems with women, Raj can´talk with them and Howard still living with his mother (a really gelei mother, door the way).
But why are they just like husband and wife? In the episode 15, season 2, when Leonard´s mum appeared for the firts time, Leonard tell her about the Raj´s problem and Howard´s codition and she said: "The selective mutims and...