[@Ruby]
It's a bad pun about how his name sounds like Butter. 

and I'm fine with that too as long as she doesn't mind Casey passing her notes asking questions about vampire hunting and whether or not she's an amazon or mutant or government super solider. 

and just to keep things Buffy related here's a Buffy joke
[img]http://www.velvetparkmedia.com/sites/default/files/u4470/Screen_shot_2012-11-08_at_9.44.57_AM.png[/img]