O'Brien was hit in the head during a stunt while taping the show, a rep from NBC told TMZ Friday.
"Tonight, NBC will broadcast a repeat of 'The Tonight Show with Conan O'Brien.' Conan hit his head doing a stunt and and the show was not finished," the rep said.
O'Brien also issued a statement through NBC saying that he was taking the incident lightly.
"Last thing I remember was enjoying the play with Mrs. Lincoln, and the next thing I knew I was in bed being served cookies in juice," O'Brien's statement read.
O'Brien was examined Friday at a hospital. NBC declined to comment on his condition.