House and Cuddy together somewhere (in the tram - when we had the bus on the end of 4th season - in a restaurant, Cuddy is running for the House out of the hospital), a car runned over them, House is unconscious, Cuddy is crawling to him, it looks like House is dead, so Cuddy kiss him, suddenly the Sleeping Beauty is magically waking up, but he doesn´t remember nothing. Last memory is when he had old team (I´m trying to incorporate Chameron). House has big psychological problems, and then he´s imagining Cuddy in erotic image and suddenly he´s remember that he slept with Cuddy, and we know they to slept together before the crash.

That´s my theory, and I quite like it.
I´m sorry for mistakes, I don´t speak English so good. And I´m sorry for the theory too :D
And another one sorry : If it´s in bad category, I´m really sorry too.