At the Halloween dance party, Mal Duncan tells Connor his costume is "Superman done right." In the comics, that was original costume for the post-crisis Superboy (Conner).
As part of the practical joke on the high school by student Marvin White, in the Batman costume, Megan takes the image of Loony Tunes' "Marvin the Martian." Loony Tunes, like DC Comics, is owned by Warner Brothers.
The magic store "Abel's House of Secrets" references the mystery/horror anthology title "House of Secrets" published by DC from 1956-1978, where stories were presented by the two residents of the house, Cain and Able.
At the Halloween dance, a comment is made about the Martian invasion being a "Halloween cliche'". This is a reference to the War of the Worlds broadcasts, by Orson Wells and others, which have caused panics by radio listeners at least three times since 1931.
The events depicted occur on October 31st.