THE TIMELY TIMES magazine on the news stand is a reference to the highly popular TIME news magazine; founded in 1923, it is published in New York City, the home of the Ninja Turtles.
The "Modern Barbarian" comic on the news stand foreshadows the coming of "Crognarg The Barbarian", a fictional cartoon series in this Teenage Mutant Ninja Turtles' universe. The barbarian is an homage to the 80's cartoons Thundarr the Barbarian (1980) and He-Man and the Masters of the Universe (1983).
The CORPS CADAVERS comic Donatello reads while teasing Leonardo about Karai is the same comic Raphael reads while teasing Donatello about April in an earlier episode titled Monkey Brains (2012).