Mary arrives and tries to snap Sheldon out of his funk but it proves a trickier task than expected.
Upon her arrival, Mary decides to cook a communal dinner for the guys and neighbour Penny (Kaley Cuoco).
However, Sheldon stays in his room away from the group, still annoyed Leonard employed his mother to try and help him out of his current state.
So when does the continuity error occur? Well, it comes when the group hastily forget to say grace before tucking in.
