"Cartoon Network must apologize and also commit to pulling episodes that desecrate black historic figures," Sharpton, a civil-rights activist and former Democratic presidential candidate, said in a statement Tuesday.
"We are totally offended by the continuous use of the n-word in (cartoonist Aaron) McGruder's show."
The episode, "The Return of the King," aired Jan. 15, the day before the national holiday honoring the slain civil-rights leader. It shows King emerging from a coma and using the n-word in an angry speech venting his frustration toward sexually explicit hip-hop videos, among other things.
In the episode, King is branded a traitor and terrorist sympathizer for his "turn-the-other cheek" philosophy of nonviolence in response to post-Sept. 11 retaliation. Exhausted, he moves to Canada, but his speech provokes a second civil-rights revolution.
Cartoon Network released a statement Tuesday saying the episode is a tribute to King and "in no way was meant to offend or `desecrate'" his name.
"We think Aaron McGruder came up with a thought-provoking way of not only showing Dr. King's bravery but also of reminding us of what he stood and fought for, and why even today, it is important for all of us to remember that and to continue to take action," the statement said.
McGruder, who has been called a "genius" and "the angriest black man in America" as he skewered everything from the Bush White House to Black Entertainment Television, began writing "The Boondocks" comic strip, on which the TV series is based, in 1997.
The strip, known for its risky political and social satire, follows the adventures of two black children living in a white, middle-class suburb.
Sharpton said he could appreciate McGruder and his achievements, but added: "This particular episode is over the line."
"The Boondocks" airs Sundays at 11 p.m. EST on Cartoon Network. It is the centerpiece of the Adult Swim late-night block of programming.