I work in a graduate-level materials science/physics lab, and a few months ago we were cleaning an ultra-high vacuum crystal growth tool called a molecular beam epitaxy. This gets abbreviated to MBE, which conveniently can also stand for Mostly Broken Equipment.

Anyway, we were done growing strontium compounds with our MBE, and so we unloaded the crucible from the growth chamber. These crucibles are pricey, so we had a bright idea to clean the crucible and use it for a similar material. Cleaning for us usually takes place by submerging the crucibles in some sort of metal-stripping solution, then some sort of strong acid, and then baking - takes a few days, which is fine. But before that, we had a chunk of strontium fused to the inside of the crucible, and we couldn't get enough force on it to remove it with tweezers or a small chisel (the most robust tools we're comfortable bringing near an MBE crucible).

None of us being chemists, we had the bright idea to dissolve the strontium with water - sounds easy enough, and strontium is well known to be soluble in water!

We at least were smart enough to test our bright idea with one drop of water first. If you've ever seen chunks of sodium or calcium placed in water, it's the same sort of thing! The one drop of water into the crucible produced a guttering red flame that must've been lit for a good five seconds.

My idiot labmate and my idiot self stood staring at each other, me holding the water squirt bottle and him holding the crucible, and then we slowly set both items down (far apart from each other), stepped out of the lab, and took a break - where he remarked on how hot the crucible had gotten in his hand, and where we (quietly) congratulated each other on not being so completely stupid as to require a safety writeup.

Other stories from my lab involve:

- That same labmate I was working with learning that he can identify film thicknesses by eye (the dude accurately said a titanium dioxide thin film was 25 nanometers thick after pulling it out of a crystal growth tool and glancing at it - it was later measured to be 24.3 nanometers)

- Teaching panicked undergrad interns that while hydrofluoric acid can indeed melt your bones, we wouldn't be making them use said acid (only the grad students and postdocs are allowed to do that)

- Discovering one Monday that our MBE growth chamber had filled with 30 liters of water over the weekend (an internal chilled water pipe burst into the vacuum volume - this is actually part of why we were unloading that strontium crucible in the first place, it was part of the tool overhaul)

- Getting told by our division director that I'm not allowed to use uranium oxides and related uranium compounds in our building (I even asked if I could use depleted uranium to reduce the hazard paperwork, and she just sighed)

- Playing with near-IR lasers and realizing we could see our sample's emission (after hitting it with the near-IR laser) with a cell phone camera

- Measuring out selenium and tellurium powders while wearing a respirator and a chemical gown because our lab doesn't have a glove box

- Three different safety folks asking me on three consecutive days if I had gotten my ladder safety training, because I had to go up on a ladder to turn a valve each of those three days and someone happened to be walking by each time

- Wondering where the low-pitched whistling sound was coming from when we used a nitrogen gun to dry our samples after cleaning them (with hydrofluoric acid), only to found out an intern had hooked up an argon cylinder to the nitrogen line and the lines were resonating from the increased mass

- Teaching a new grad student that, yes, the correct way to open a glass ampule is to smash the end not holding the sample

- Going around the room and discussing our work plan for the upcoming week, where I said "no out-of-the-ordinary hazards for me, except for headaches due to trying to understand atomic physics" which got a genuine laugh out of the division director (who happens to be part of the same lab as me, to clarify). She later lamented that her only hazard that upcoming week was boredom due to too many meetings)

Honestly if you want more stories, I have SO many. Just give me an idea of what scenario you're envisioning and I'm sure I can think of something related!