Just about the greatest comedy routine ever, by comedians Abbot and Costello, with Abott telling Costello the names of the players.

In this context, the first baseman is named "Who"; thus, the utterance "Who's on first" is ambiguous between the question ("which person is the first baseman?") and the answer ("Who is the name of the first baseman.").
"Costello: Whats the guy's name on first base?
Abott:What is the guy's name on second base
Costello: Im not asking you Who's on second!
Abott: Who's on first!
Costello: I dont know!
Abott: He's on third, we are not talking about him."

"That Who's on first? Routine always makes me lol"
by AJ Molina October 20, 2008
Get the Who's on first? mug.
the most basic of facts (from Who's on First?, a confusing comedy routine that was done by Bud Abbott and Lou Costello)
Apparently, most politicians don't even know who's on first about citizenship.
by The Return of Light Joker April 8, 2009
Get the who's on first mug.
Han Solo shot first.

Who shot first?" is a phrase used by Star Wars fans to refer to a controversial change made to a scene in Star Wars Episode IV: A New Hope. In the original theatrical version of the film, Solo shoots Greedo under the table and Greedo dies without firing a shot. The scene was modified for the 1997 re-release to feature Han using his weapon in retaliation after Greedo fires at him; the latter rather implausibly missing Han at point-blank range (<2 meters away). Thus, the phrase "Who shot first?" is a retort to director George Lucas' explicit cinematographic assertion that "Greedo shot first.
Peter: I saw episode IV the other day, and I swear Greedo didn't shoot first in the original. Who shot first?

James (fanboy): Han Solo shot first.
by Lethan November 13, 2010
Get the Who shot first? mug.
A reference to the Star Wars controversy where it is debated that Greedo shot first before Han Solo. This is used in a way to define something that will become an arguement of what happened first.
Person 1: Actually no, i was just copying FPS Russia
Person 2: FPS Russia?
Person 1: Yes
Person 1: Look him up
Person 2: Never heard of it.
Person 1: Gilbert: On youtube
Person 1: It's a person
Person 2: Is it a rip-off of FPS Doug?
Person 1: No
Person 1: he copied his friend fps kyle
Person 2: Okay then...
Person 1: What?
Person 2: Not getting into an entire "who shot first" with FPS titled vids on youtube.
by tbclycan April 30, 2011
Get the Who shot first mug.