And a bit more recently in my campaign I've had another instance of this happen. Nerrath Ap Jerran, a young, capable and wholly evil arcanaloth sorcerer in Sigil. While not a BBEG, but rather the "apprentice" and overall chewtoy/cabinboy for Shemeska the Marauder, Sigil's King of the Crosstrade, and my namesake, he was an interesting character. Then one of my players starts referring to him as "Jingleballs", referring to his mistress making him wear a belled collar, and a possible inference about his repertoir of piercings.
Bam, there goes his credibility in an instant and he's stuck for all posterity to be referred to as "Jingleballs". *facepalm*