In the episode where Homer becomes a boxer (sorry, I don't know which season it's from), near the beginning is a scene where Homer and Moe are talking in the women's toilet in Moe's Bar. On the wall are several posters depicting Moe during his boxing career. On one of them, it says "Tonight: Syslak vs. Oakley". Bill Oakley is an executive producer on the show, so this is a reference to him. I apologise if this is elsewhere on the site, but I did check and couldn't find it anywhere.