Ran Ran Ru (ランランルー, Ran Ran Ruu) is a dance move performed by Donald McDonald, the Japanese interpretation of Ronald McDonald, in a commercial for a mid-2000s McDonald's advertising campaign known as "Ronald Rumors" (ドナルドのうわさ, Donald no uwasa), where he answered questions about himself.
The move is done in three steps:
The move became a staple parody of fan artists, especially in Japan, with the Japanese video sharing site NicoNico being a particular hotspot for parody videos. One such video would have him do the dance in tune to Flandre Scarlet's theme "U.N. Owen was her?" (referred to as McDonald Insanity or McRoll'd), which would go particularly viral and have Donald associated with Flandre.
The advertising campaign would feature other commercials that would similarly go viral, such as him showing a different dance, him posing in front of a mirror, him falling backwards on a park bench after taking a phone call, and him playing baseball.
On Danbooru, this tag is primarily used for any character seen to be performing or demonstrating the Ran Ran Ru dance, but references to the other commercials in the Ronald Rumors campaign can also be tagged with it.