This year, Camila Mendes and Lili Reinhart, who play Veronica and Betty on the show, respectively, dressed up as characters from Napoleon Dynamite. Mendes dressed as Pedro and Reinhart as Napoleon himself. They recreated the iconic shot of Napoleon and Pedro prepping to campaign for class president. Napoleon, if you remember, wore a "vote for Pedro" shirt, while Pedro wore a blue chambray shirt with a bolo tie. Vote for Pedro and all your dreams wildest dreams will come true!
Meanwhile, Cole Sprouse, who plays Jughead on the show, dressed as a minion (those yellow pill-looking things from Despicable Me) with a sign that read "stop sexualizing minions." I guess he's fighting against rule 34; if minions are this ubiquitous, then there's got to be sexualizing of minions somewhere on the internet. Good to see Sprouse is fighting the good fight. See his costume, below, moments after Reinhart does a portion of Napoleon's dance.
The Riverdale castm in particular, is a kind of pop culture ouroboros, as the show itself it swathed in current references, but the cast revels in '00s nostalgia, starting with the appearance of one of the decade's true child stars, Cole Sprouse, in the cast. They lead pop culture because they're on one of the most popular teen shows around. They also comment on pop culture by being, well, millennials who grew up under the leadership of movies and TV.