Longest I've lectured is about half an hour. The full class is probably 100~150 students.
That's a big class. If you accept this mission... you could be helping those 150 students see video games in a new way. It might be interesting to start by asking them what messages they think video games deliver (about the representees or absence of them). What is the actual course called?
Sounds like the Computers and their Impact on Society class everyone had to take when I was an undergraduate. Everyone had to give a lecture. It was at 8 in the morning, and this was a commuter school so everyone had to wake up at wtf in the morning to make it. Because of that and the fact that absolutely no one wanted to take the class, you lost a letter grade every time you were absent. I talked about free software. Someone actually said "but that's communism! That's not how we do things in America!" out loud and I couldn't think of a response other than "that might be the dumbest thing anyone has ever said to me." The professor laughed his ass off and called me 'Comrade bfv' the rest of the semester. Hated that class.
That sounds way worse than my class, haha. Luckily not every student does a lecture in this class, the Prof. just approached me because he saw some of my gaming stuff (I have no idea how he found it, actually). Brb making a Hubskina character named "Comrade." He'll be a pirate.