My worst was seeing my sea squirt in the overflow one day, and thinking, I might just leave him in there to do some cleaning... I was actually just lazy and didn't want to raise the lights and fish him out. Well, he crawled 1.5 feet up the overflow tube, and wedged himself in the bulkhead, just enough so you could see his bottom slightly protruding from the top, but not enough to grab hold of... anyway needless to say, the sump drained into the display, overflowed into the lounge room. I had to remove the plumbing on the bottom of the tank, and there was Mr. Squirt poking out. I could not get a proper grip to pull it out, so a friend got under there and grabbed it with both hands and we all pulled.. he popped out, and it was very messy. It was actually very funny afterwards with the image of my friend a female friend holding it with both hands, and it squirting her in the face. About two years later, I run the return pump high in the sump, and Mr. Squirt (yup the same one) gets removed from the overflow straight away if he wanders in there.