Sheldon was reminding the guys what happened September 22, 2007. It was also the anniversary of the death of Dr. Seuss. Sheldon recited the memorial poem he wrote that day to honor Dr. Seuss. 

Sheldon remembering Dr. Seuss.

Why die?
Why did he die?
Old told.
I was told he was old.

Community content is available under CC-BY-SA unless otherwise noted.