The Blue Monkey is a 1920s-style bar seen in the episode "Jack and the Gangsters." The bar serves as a hub for criminal activity, seen in the form of sketchy-dealing robotic assassins and notorious gangs who "run things around the town." The bar also has a rather sizeable group of armed security guards, further suggesting that the bar has criminal associations.
The name of this bar is taken from the one in the fictional movie, Angels with Even Filthier Souls that Kevin McCallister watches in Home Alone 2: Lost in New York.
It is unknown how the destruction of the past Aku affected the existence of this premise in the future.