DY: Meant in good humor is irrelevant. The worst of insults are often meant in good humor. Taken in good humor might change things, but how can you say that L’mafrea whether or not your action was Assur depends on if he cares or not? Maybe if you know each other well and know that this insult isn’t an insult it’s okay (there seems to be a wide number of Shittos about nicknames and whether it’s okay even if he’s Mochel and presumably it’s the same issue).
Also, I’m amused that McDonald’s and Hershy’s [sic] are equated.