in the chapter where vivian joins the party, mario loses his name and body and vivian is the only one who cares enough to help him while the other party members dont believe mario is himself. vivian being trans is thematically important to the story
There's a one in a million chance for Lancer to appear as "Lancer (Green)" in the KEY ITEMS menu in Cyber Field, with an emblem similar to Whatsapp (the app) on his stomach, while also being green. He also says "Hey! Whatsapp?" in reference to the app.