When Slacker Batman pours cheese over his nachos, a cartoon mouse in a superhero costume is visible on the bottle. This is Little Cheese, the Micro-Mouse. Little Cheese was a character produced by DC Comics in the 80's and appeared in their title "Captain Carrot and his Amazing Zoo Crew". The Zoo Crew was a team of superheroes who lived on the alternate Earth-C populated by cartoon animals.
The first riddle posed by Riddler to Booster Gold is the well-known "Riddle of the Sphinx" from Greek Mythology.