I'm doing a Big Bang that's an AU of S4 (no demons, no angels, basically nothing in canon happens post S3's NRFTW) and Sam's the one who hauls Dean out because that's the way my fangirl heart wants it to be. In any case, Sam will totally be celebrating Dean's birthday in my BB because the guy's awesome and he's turning the big 3-0 (even though he's completely emotionally shattered, was half feral and is barely functioning).