"Toughest class" turns out to be the easiest

I've had this happen on a few occasions, one recently, and I'm wondering if anyone has had this too.

I'll walk into a room, and ask literally any staff member, generally a neighboring teacher, how the class acts, or how does their teacher talk about them. And it's by the immediate reaction I get an idea. Some know the class is well behaved, some say to watch out for some students, and some just chuckle at me knowing I'm in for a tough day.

This happened to me recently, and even in the sub plans it stated to be firm with the kids in periods 3 and 4, and that they will walk over you. 2, 5, and 6 will have little to no issues. HOWEVER 3 and 4 were my best classes and I had little to say about them. They even had two other adults in the room who both told me they don't do well with subs....but the day went fine for those "tough" classes. Anyone else have this happen?