)
You have to know a specific line from the first TMNT movie,and who the two characters are. Also some knowledge beforehand of what crumpets are and what cricket is and the American biases against British things we think sound funny.
Casey Jones ion the left is dressed in an outfit that went unused in the recent MMPR/TMNT comic,and on the right is Venus from Ninja Turtles Next Mutation,a show produced by the same people as Power Rangers.
Now laugh,dammit.