Hal: Do you... remember that big "G" he wore on his jacket?
John: Do you remember what Guy said it stood for?
Geoff Johns was actually able to work in a joke made in The Simpsons Movie that "EPA" was a sound effect made in Green Lantern #25 when Sinestro threw Hal Jordan into a vat of acid. In the actual issue #25, one of the final issues of the crossover, there is indeed an "eee-pa!" sound effect during a battle between Hal and Sinestro. (No vat of acid, unfortunately.)