The electrical wiring in this house never ceases to amaze. Almost always to code, but just really creative. We're updating the office so I can actually use it since I'm working from home full time for the foreseeable future, probably until we move at any rate.
They have two lights and a fan in the ceiling, which we're replacing with 2 lights and then one light, on separate switches. The two lights are on a 3 way switch, with the lights after both switches. But that's the normal part. They used 3 wire cable from the box with the fan and light switch, and used the red to run straight through all the lights and feed the fan, so they only had to run one cable. It makes sense and might be super common, I dunno, but it looks confusing as hell when you pull all the lights down and try to figure out what's going on.