About

Captain Obvious is a pejorative nickname given to a person who insists on stating things that are patently clear.

Early Appearances

The widespread use of "Captain Obvious" among English speakers predates the widespread adoption of the Internet.

One early appearance of the phrase is found in a 1998 Study guide by David Groth. A+: Core Module Study Guide

Excerpt from page 189.

The larger of the two specifications is known as Wide SCSI-2 because it's wider (Captain Obvious rides again).

Source: Wiktionary

The same year, there was another Captain Obvious mentioned on alt.religion.kibology on Usenet. (Link)

In December of 2006, RealClearPolitics writer Robert Tracinsky wrote The Return of Captain Obvious in which he recalls seeing a comedy troupe that performed a skit of the same name during his days at the University of Chicago some time between 1987 and 1991.

Film

The phrase is spoken in the 2000 film Dude, Where's My Car.

Excerpt (courtesy TVtropes.org):

Mr. Pizzacoli: They said "the Photon Accelerator Annihilation Beam," you fool!
Chester: Hurry, activate it, dude!
[a small panel on the Transfunctioner reads "Photon Accelerator Annihilation Beam"]
Chester: I think that's it, dude.
Jesse: Thank you, Captain Obvious!

Online

Because the term has been a common part of spoken slang for many decades, the term has also been used online in the form of text and in image macros.

Uncyclopedia and Urban Dictionary are known of comparing this fictitious superhero to real-life figure John Madden, known of stating obvious and unnecessary information.