When we have been sick for quite some time and suddenly we start feeling better, it really puts us in a good mood. Apparently, that is the way that Sheldon is feeling and he comes out of his room as a “little ray of sunshine.” The problem is, he was such a pain when he was sick to everyone that nobody wants to celebrate along with him.
In order to let him know exactly how difficult it was during the time he was sick, they flashback to his recent illness. He had the flu, and he went out of his way to offend everyone in some way or another. From offending Penny when she wouldn’t run Vicks on his chest to getting in a really good zinger on Raj and Emily, it seemed that he was on a roll but nobody appreciated it.
Now that he is feeling better, it seems as if he would be better off just going back to bed. Fortunately, he has his good friends there to let him know exactly how much of a pain he was while he was sick.