1979 saw the revival of the Star Trek franchise with Star Trek: The Motion Picture. McDonald's was part of the marketing blitz. It tried to draw in kids by offering Happy Meals inspired by the movie and its fresh take on Star Trek. The box included a connect-the-dots game, corny jokes, and puzzles.
McDonald's commercials pushed this Happy Meal option. One of them used a Klingon as a pitchman. The narrator offers a translation, but the character is not actually speaking Klingon--just gibberish. He's assuming that no child who was watching would know the difference.
You can see more photos of the Star Trek Happy Meal and another commercial in the series at Flashbak.