Origin:Unknown
Year published: 1996
"I see what you did there" is used to notice ones cleverness (usally involving a joke)
Example #1 -
Me: 8===D, "Why the long face?"
Random person: "I see what you did there"
Example #2:
Me: 8===D, "Its an alien smiley face!"
Random person: "I see what you did there"
(sorry for the immatutre jokes)