Ose

In the Persona games, there's a persona called Ose that is only weak to light and resists physical. Joe got it in a fusion accident, which is an event with a very low chance of happening. When he got it, it knew loads of really strong moves and it was much higher level than the rest of his personas. On the spot, Joe decided that he would keep Ose on his team forever, which you're not supposed to do with Personas.

by Jelly.

After using Ose for a while, in an attempt to mock people in chat, Joe started saying, "You're only winning because of Ose, Joe" in a strange voice which sounded like an old-timey radio announcer. He hadn't even seen anyone in chat saying this, so he was just saying it as a blatant strawman complaint on purpose. He had done this voice to mimic people in chat before, but this was when it had its most use. Ose also had a really high luck stat, and that actually affects things related to chance outside of combat. This made Joe also start saying the Ose line whenever something lucky happened to him.