At the start of the 'intervention' Penny and Howard move down the couch twice.
As initially noted in this episode, and continually referenced throughout the series, Penny's car is displaying a check engine light. The car is seen to be a Mk1 (first generation) Volkswagen Rabbit Cabriolet, sold in the US in the early 1980's. This vehicle does not have an on-board diagnostic system, thus is not equipped with a check engine light.
In the reverse camera view of the apartment (when the group gathers for Sheldon's intervention) Sheldon and Leonard's desks are placed flush against the wall. In the normal angle, their desks appear to be in the middle of the room.
It makes no sense for Sheldon to lash himself to a bus seat because there are no safety belts. A bungee cord will not improve safety one bit since even in a low speed impact, the body's momentum is far to great to be restrained even by multiple bungee cords, which even far lesser physicists would know.
When asked what color car Sheldon wants, he responds that he wants one that's the pale blue of Luke Skywalker's light saber. This is actually a mistake, as Luke's light saber is green. The pale blue light saber was actually Anakin's, Luke's father. But technically he is correct it was Lukes (even though it was his fathers first) since Old Ben (Obi-Wan) gave it to him he did use that one until he made himself a new one that was green.