Martha headed straight for the console, and turned back halfway there when she realized the Doctor wasn't with her.
He was leaning against the door, with a strange, dreamy smile on his face. Martha couldn't help but smile herself as she strolled back to him.
He focused on her when she was right in front of him, but his smile only widened. "Martha Jones. Do you realize who we just met? Right here in my TARDIS?"
She'd never suspected the Doctor would get quite this sentimental about kids, even--well. "Jack's baby?"
The Doctor shook his head, "No--well, yes, but--did you hear what Jack called him?" Before Martha could say a word, the Doctor answered himself. "Indiana. Indiana Jones! We just met Indiana Jones!"
Martha took a half-step backward. "What, like the films?"
The Doctor was staring over her head, and he waved his hands in dismissal. "No, no--yes! But no--every Time Lord who comes to Earth in the late Twentieth or early Twenty-first thinks they've discovered some grand anomaly, because those movies had faded into utter obscurity by the time Jones was born. And all this time it was just Jack Harkness and his refusal to stop making cultural references to things no one around him remembers!"
"So you're saying he's going to be famous," Martha interpreted, waiting for anything more intelligible to fall out of the Doctor's mouth.
"Famous, infamous--ha! I should have known Jack was related to him--only all of his descendants are rather pointed about the Jones, and you never think of someone like him being anyone's little boy. And I shook his tiny five-year-old hand! And showed him his very first TARDIS! Indiana Jones!"
Martha nodded slowly, and gave up on the Doctor spontaneously starting to make sense. "If he's so famous, wouldn't Jack have heard of him? Is that going to be... weird?"
The Doctor hesitated for a moment, frowning, but shook his head. "I shouldn't think so. He was only really famous on Gallifrey, and only among certain circles, at that. His book was never translated out of Gallifreyan--it couldn't be, and still mean anything. I don't suppose Jack will even be able to read it." The Doctor frowned a bit harder, and then shook it off. "I'm sure Indiana will explain it to him, anyway."
"He wrote a book," Martha said, and then shook her head quickly. He was five years old; she doubted he could write his name. "He's going to write a book, in Gallifreyan."
The Doctor finally seemed to realize that she had no idea what he was talking about, and nodded quickly, walking briskly toward the console. "The most-read book written by a human on Gallifrey. It's--well, it's difficult to explain, because it was written in Gallifreyan, about Gallifreyan--about the tenses, mostly, which are ... complicated. The linguistic analysis was almost completely specious, but it was a scathing critique of the Time Lords, and also made you hurt yourself laughing. It was banned instantly, mostly on the grounds that a human couldn't possibly have written it, even though a panel of Time Lords had certified his fluency in the language years before."
"Which is how it got so widely read?"
The Doctor nodded, setting their coordinates. "You can't actually admit, past your first fifty years or so, that you want to study humans because Indiana Jones was so... so cool. But that's why a lot of us did, anyway."
Martha joined him at the console. "So... is becoming your hero's hero like becoming your own grandfather?"
"No, no--ewwwwwraaagh," the Doctor shook all over as he said it, like a dog shaking off water, wrinkling his nose and screwing up his mouth. "God, no--you've never met my grandfather, but no, decidedly not."
The Doctor twirled a dial, and the TARDIS started up.
"Mind you," he added meditatively. "If Jack weren't how he is--which he got to be because of Rose, which is to say because of my TARDIS, so because of me--Indiana wouldn't exist at all. So if you believe the stories about my great-grandmother, I suppose I might possibly in some sense be my own great-great-great-grandfather. But that's safely remote, don't you think?"
Martha rubbed her forehead--her eyebrows had gone as high as they could get, and she was going to give herself a cramp. "If you say so."
"Right," the Doctor said, as the TARDIS quieted. "Here we are, Indiana Jones's sixth birthday. Do you suppose he'd like a tour?"