My math teacher in 10th grade was the best at this. Someone knocked over a huge box of markers and he just grabbed paper towels, tossed some to us, and made a joke about graphing the mess. He turned a whole cleanup into a team thing in seconds, like violap42 said about laughing it off. Honestly set the vibe for the whole year after that. What's the funniest save you've seen?
But what if turning everything into a joke isn't the right move? I once saw a teacher make a pun after a lab accident and the whole room went silent. Forced humor can make students feel like the teacher is just putting on a show. That kind of save might work for some, but it risks coming off as insincere. A calm, direct response often fixes the problem without the cringe.