Synonymous with "Ridiculous" i.e.
Crazy/Bizarre/Extraordinary/Outrageous
Usually "Redonkey Kong" is used as a positive expression, applied to something perceived as good, usually surprisingly so. Though it can be used in special circumstances that are outrageous, even in a negative way.
Made
popular by the Hit television show "30 Rock" in the episode "The Source Awards", although in the show it is implied that Redonkey Kong is the alias of a fictional musician that has a beef with Tracey
Jordan.
Despite Redonkey Kong being debuted on 30 Rock its origins are unknown. Though it can be assumed it came to be due to the similar
sound of "Redonkey Kong" to "Ridiculous". Also, the iconic
game Donkey Kong is, itself, Ridiculous.