Curses is improv speaking, it's still probably my favorite party game, mostly because what you say doesn't really matter once the game really starts going.
Like most casual party games, the rules are incredibly simple. Every turn has you drawing a Challenge card, doing what it says (e.g. "Give a news report" or "Explain the difference between Coke and Pepsi") and then drawing a Curse card and giving it to someone else to do what it says (e.g. "Don't bend your elbows"). The Challenge cards are only for a single turn, but the Curse cards last until you get caught failing at it. If anyone else notices you not following a Curse, they can ring a bell and call you on it, at which point you will flip over the card and be free of that curse. A player is knocked out after three failed curses and the last player remaining wins the game.
This is one of those games where it's most fun if you don't play to win, but instead you play to make awesome/terrible Curse combinations. A lot of the Curses build off each other so you can get a Curse chain going around the table until someone fails. For example, there's a curse that makes say a pizza topping whenever someone stands up, another that makes you howl whenever someone says a food, and another that makes someone clap whenever someone makes an animal noise. Alternatively, you can give someone a theme of curses, so one person has to speak in a French-Irish Vampire-Pirate accent anytime they talk. Of course, as with most games that make people talk in certain ways, most people stop talking when those start appearing, which is precisely why the Challenge cards are so crucial and why the content of your response to a Challenge card is so meaningless. It's not about what you say, you just have to say things to activate all the curses on the table. Admittedly, this makes the first round kind of lame since there aren't very many curses on the table, but you could always fix that by just evenly distributing at least one curse card to every player.
The game is designed for 3-6 players and lasts between 60-90 minutes (in my experience). You could easily play with more players, but it will not only take longer since there are more players to eliminate, but it will also be much harder to keep track of what everyone is supposed to be doing, so it'll be easier to not get caught when you slip up doing a curse, which is only going to make the game last even longer, so just keep that in mind. This is definitely a great game if you want to laugh a lot during your game night.