Everyone's got one, I'm sure. For instance, just last week I broke an LJ 4000 while replacing the transfer roller. If you are all through laughing, what happened was that I was sliding the new roller into the white nylon bushing at the right side of the printer, when the guide that helps secure the bushing, nearest the registration assembly, just broke and fell over.
Previously, I had always believed that I could even train my cat to replace a transfer roller. Maybe the cat would have done a better job. I ended up pulling the top covers, the Tray 1 pick up assembly, and the registration assembly just so I could get a good look at the damage. And then I glued the broken guide back into place. See, Loctite has this really effective two part adhesive for plastic...
Actually, after I opened up the printer, I found a lot of broken plastic and missing parts (such as the spring in Tray 1), so I could only conclude that some truly ham-handed guy had serviced the printer at one time.