Making another class see sideways

So in class we decided to do something random and that was to flip all the desks in random places and stack others as sculptures. This was just to see the next class reactions to our actions. I personally felt bad as we were doing it and probably would've never done it if no one else did. After it was complete the room looked pretty crazy and I thought the next class would do nothing but laugh at the whole situation. But as we were leaving there were some students for the next class and they were mad that we were just leaving and not putting any of the chairs back in their standard positions. I felt bad as we just walked away as they were wanting an explanation. I think that since the first couple of students were upset with our actions, that their attitude spread through the rest of the students that came in for the next class and they all became very angry with our actions. I think any kind of mood is contagious whether it be positive or negative. We probably put that whole class in a bad mood and it probably wasn't the most pleasant class in the world. I think we should probably do something in a form of an apology or an explanation of our actions. I say we just write really big on the dry erase board that we're sorry or something silly like that.