Sudden Someone

Can be describe as a person, either in real life or online, that tends to show up out of no where and say the most smartest or oddest thing or even something straight out savage. They're also known for having odd but fairly reasonable mood swings and will be or are most likely a drinker.
It can also work for someone you know that is indescribable or mysterious in your friend group, but also super chill.

Dang, Kyle. I didn't expect you to roast Jimmy like that. You're like...a sudden someone.