Michael picks up a doll of Krang from Teenage Mutant Ninja Turtles off of the mantel above his and Ben's fireplace, then has a conversation on the couch with Ben, he places the toy on the table, then when they start making out the toy is seen in the background on the mantel above the fireplace again.
When Justin enters the comic book store, an Interac sign is clearly visible on the door. Interac is a debit card network only available in Canada.
When reconnecting with Brian, Michael tells Brian how he and David don't share an affinity for comic books, citing Batgirl's crippling at the hands of the Joker as one example. But a comic book aficionado like Michael would be aware she was crippled because the Joker shot her in the abdomen, not because he raped her (which never occurred in the book, "The Killing Joke", that plot point occurs in, though he does photograph her nude to torture her father, Commissioner Gordon).