If you've ever spoken to Mr. Wallet in depth, you'd probably know that he speaks Japanese semi-fluently because of his "soul searching" ventures.
Well, I tried to get him to teach me Japanese during my "soul searching" venture and at one point I asked him a very important question. The conversation went something along the lines of:
"What's the difference between Senpai and Sensei?"
"A Sensei is a teacher and a Senpai is an honorary term for an instructor."
"So can I call you Wallet-Senpai?"
"I'd rather be punched in the face but sure."
And he was Wallet-Senpai ever since.