[Well, you wouldn't be you if you weren't pushing the subject. And so Birthday is forced to make another decision: he shakes his head a little, crossing his arms.]
It's not that I don't want to tell you! I just don't know. [He waves his hand, apologetically dismissive.]
I've never seen you trigger it, so I don't know what does it! So I can't tell you, either. Sorry. [The apology is tagged on, quieter than the rest, as he hopes, hopes that this sounds plausible and that you'll believe him. It's not like they usually end up in the same fights, anyway, so maybe Art will swallow this story. Or maybe not, but at least he tried.]