Brooklyn is the most populous and second largest of the five boroughs of New York City, bordering the borough of Manhattan across the East River. It is a recurring location in the Teenage Mutant Ninja Turtles multiverse, usually as the birthplace of Casey Jones, and sometimes the location of the Second Time Around building (which in other incarnations is located in Manhattan).
In some versions of TMNT, Casey and Raphael are portrayed speaking strong Brooklyn accents, while April O'Neil, Splinter, Leonardo, Donatello and Michelangelo do not.