Where did Lucas come from?

It all started when Lucas was getting dressed for bed. He had just had a bath and I was saying, rhetorically, "Where did you come from?"

Lucas: I came from Saturn, I mean Jupiter.
Me: How did you get here?
Lucas: I came in an airplane.
Me: Did you come here by yourself in the airplane?
Lucas: No, I came down with Spongebob and Patrick. Patrick flew the airplane and I helped with the brake.
Me: That's an important job, knowing when to brake when you're in an airplane.
Lucas: Yeah, that's what I did.
Me: So how did you end up at our house?
Lucas: I'm going to tell you a secret...I popped out of a hole (!)
Me: Really, what hole?
Lucas: [walking over to the window and looking out] A secret goblin hole. I'll show it to you tomorrow.
Me: A goblin hole, with real goblins?
Lucas: Yeah, and you want to know something else? There was a witch in there too. But she wasn't a bad witch, she was a good witch.
Me: Wow, I'm interested to see what this goblin hole is all about.
Lucas: And I had a stick in the gobin hole, to protect me from the goblins.
Me: And what about the witch?
Lucas: I protected her too. And then, when it was time, I popped out of the goblin hole.

So this morning, I asked him to show me the goblin hole. He seemed not to remember the conversation from last night.