The phrase take me to your leader is the demand that a humanoid from outer space conventionally makes to the first human being, or animal, it encounters after alighting from its flying saucer.

According to The Yale Book of Quotations (Yale University Press, 2006), edited by Fred R. Shapiro, this phrase may have originated in a 1953 cartoon by Alex Graham:

Alex Graham
Scottish cartoonist, 1917–1991
1 [Addressed by two extraterrestrials to a horse, with a flying saucer parked in the field behind them:]
Kindly take us to your President!
New Yorker, 21 Mar. 1953 (cartoon caption). Apparently the source of the science fiction catchphrase, “Take me to your leader.”

However, the text in which occurs the earliest use of take me to your leader that I have found seems to ascribe the origin of the phrase to “the Man from Mars” who addressed “one of a herd of cows in a field”—but I have not found out what this refers to; the text in question is the following unsigned article, published in The Augusta Chronicle (Augusta, Georgia) of Thursday 9^th August 1956:

When a feller needs a friend
(The Birmingham News)

They just won’t let a boy be a boy. You take Jimmy Blackmon, 17 years of age, known in Charlotte, North Carolina, we suppose as the local Wernher von Braun.
Jimmy built a six-foot rocket powered by liquid oxygen and a fuel injection system. We suppose we should be surprised by this—that at such a young age he could construct a miniature version of what all those scientists at White Sands and other places such as Redstone Arsenal have created. But no, surprised we are not. Out of Space McGillicuddy TV programs, comic books and such great impetus is developed among the youth, and they propel themselves into science with a fury. Huck Finn and Tom just explored caves. Mild stuff.
But the Civil Aeronautics Authority, informed about Jimmy’s intent to touch off his rocket, allowed as how this would be against the law, a hazard to airplanery. But the Army has come up with a suggestion that maybe it can find a place to allow young Blackmon to shoot his rocket.
We’ll just say this. Somebody better do something for that boy. For all anyone knows, this is the kid’s first step toward being the first American ever to set foot on the moon. Jimmy might want to do just that, too. At least up there regulation presumably are [sic] nonexistent. But no one ever knows. You recall the Man from Mars, odd-looking chap, arriving via rocket on earth and walking up to one of a herd of cows in a field saying, “Take me to your leader.” Like we say, anything is possible and don’t you forget it.

Perhaps the anonymous author of the above-quoted article published in The Augusta Chronicle was referring to the following, reported by the U.S. publisher and humorist Bennett Cerf (1898-1971) in Try and Stop Me, published in several U.S. newspapers in March 1956, for example in the Aberdeen American-News (Aberdeen, South Dakota) of Tuesday the 20^th—I have not found out who Mike Connelly was:

Mike Connelly has a new science-fiction story. It starts with the arrival on earth of a weird space ship from another planet. The occupants pour out of it, run up to a cow grazing in a nearby pasture, and demand, “Take us to your president at once!”

The following, in which take me to your leader is used allusively, shows that it was already a well-established phrase in 1956; it is from an article in which Saul Pett, Associated Press Staff Writer, described how the TV industry overwhelmed the Republican National Convention held at the Cow Palace in San Francisco, California—article published in several U.S. newspapers on Tuesday 21^st August 1956, for example in The Corpus Christi Times (Corpus Christi, Texas):

San Francisco (AP)—Through a variety of gadgets and ulcers, the television industry is swamping this convention city just as it did Chicago last week.
You trip over TV cables in hotel corridors, you’re stopped by traffic clustered around delegates being interviewed for live cameras in lobbies, and, on the floor of the convention itself, you can’t move down an aisle without running into men carrying Martianlike mobile equipment.
One delegate, intrigued by an outer-space type of portable transmitter in the hands of a network reporter, walked up and demanded, “Take me to your leader.”

According to the following from the Riverside Daily Press (Riverside, California) of Sunday 2^nd September 1956, take me to your leader was a cliché in science-fiction stories:

The New Neighbors

Not in 32 years has our neighboring planet Mars been as close to Earth as it will be this week. Not until 1971 will it be as close again.
Mars next week will be a scant 35,120,000 miles away!
This gives a very, very eerie feeling.
We have been to the movies, we have read some science fiction.
Mars is inhabited according to the information we have thus received by little green men and luscious women.
They are zillions of years ahead of us mentally. They ride around in space ships. They hold no political conventions. They are so far advanced that they find conversation unnecessary; they read advanced minds. The Martian’s entire vocabulary is said to consist of one command:
“Take me to your leader.”
No self-respecting Martian will appear in any earthling’s science fiction story unless this statement is included.

From Channel Chuckles, by Bil Keane, published in The Milwaukee Journal (Milwaukee, Wisconsin) of Sunday 30^th September 1956, this cartoon depicts extraterrestrials alighting from their flying saucer; one of them tells a man in a TV set:

“Okay, Shorty, come out of that box and take us to your leader!”

Published in The Seattle Daily Times (Seattle, Washington) of Sunday 5^th May 1957, this cartoon is interesting because it is a human being who makes the demand to an “extraterrestrial”; in a department store, broken plates are scattered around a defiant little boy wearing a “space man” costume, to whom the manager says:

“Take me to your leader.”