I'm a pirate! Not a vampire :D
This case it's a way of telling someone lies to say you don't care about them at all.
It's meant as sarcasm, it means you don't care why they go away from you, as long as they go away.
"What should I tell her??" I don't care, tell her I've gone to the moon, tell her I've flown away, tell her I've become water and evaporated, tell her I'm invisible.
It reminds me of a joke that Daddy liked, from a guy called "Robin Harris" (Spike Lee's films).
"I like an UGLY woman!, I don't want no trouble.
Pretty women, you know how they do! '***k you! I do what I want to do!' I like ugly women, "Bitch I'm going to the moon! I'll be back in a couple of days", 'oh well you be careful now!!'"
Why do black men drive cadillacs?
'Cos you can't fit all that ass in a volkswagen.
RIP Robin Harris.
"Tell her any excuse, even, 'I've gone to the moon, so she can't find me. I don't care, just get her to go away".