Person 1 is sat on the sofa feeling ill.
Person 2 walks in with mug of coffee and trips, pretending to throw coffee over person 1. Cup is actually empty and it’s a practical joke.
Person 1 very annoyed and doesn’t find this funny.
Person 2 cannot understand why person 1 would be annoyed and thinks they are unreasonable for overreacting to a joke.
Vote YABU if it is funny and person 1 should not overreact.
Vote YANBU if it is not funny and person 2 is being a dick.