Warning(s): Off-color humor. This story is not rated "adult," but I wouldn't show it around to my eight-year-old cousins, either. Make of that what you will.
Spoilers: "Gridlock"
Disclaimer: "Doctor Who" and related characters and situations are the property of the BBC. No money changed hands and no copyright infringement is intended or implied.
Feedback: All comments are welcome.
Author's Notes: Wow, I just can't seem to stop lately. This occurred to me after watching "Gridlock" and considering a few of the logistics of a human/cat relationship, and it wasn't writen as a sequel to "Time For Everything," although they cover stuff from the same episode. As to where Martha acquires her knowledge, I'm not answering how I know that, either. So don't ask.

Martha watched from the jump seat as the Doctor ran around the console getting them set to go to their next destination. It had been quite a day, with her getting kidnapped and nearly eaten by giant crabs. The Doctor was telling her his side of the story, being as they hadn't really had time yet. She also suspected he was frantically trying to forget telling her about Gallifrey, even if she could tell it had done him good to talk about it.

"And did I tell you I met Brannigan's children? Adorable little balls of fluff. Two months old!" the Doctor enthused, pumping that one lever he always liked to play with.

"Balls of fluff?" Martha asked.

"Well, what kind of children did you think a cat would have?" the Doctor replied. "Well, a cat and his wife…so the children would be half-cat, strictly speaking. Still, it seems the feline genes are dominant, at least in the kids—"

"Half-cat?" Martha broke in. "Brannigan's wife was human?"

"Valerie? Sure! Human as you are," the Doctor grinned. "Still, didn't think that'd bother you, Martha." He seemed a little disappointed.

Martha shrugged. "Just surprised, is all. After all, I could hardly think of a cat as a legitimate partner in my time. That's just be…wrong." She shuddered and the Doctor laughed a little at that. Martha ignored him and continued. "But…if they've evolved, become intelligent enough to be equals to humans then, why not, really?"

The Doctor grinned.

"Although…" The smile on Martha's face died before it was truly born as an awful thought occurred to her.

"What?" the Doctor asked curiously. He was rewarded by the unusual occurrence of seeing Martha's skin flush dark. "Oh, now you have to tell me if it's got you blushing!" he pressed.

"Well," Martha said, trying not to come right out with it yet. "I just wondered if…if they had those children…like normal, you know? Or if they saw a Doctor somehow."

"I'm pretty sure it was normal," the Doctor said slowly. "They must have been on the road over ten years by then." The look on his face was clearly puzzled as to where all this was going.

"Ouch," Martha winced.

"Ouch?" Now the Doctor was really puzzled. Why ouch?

"Well, cats have…they have barbed penises. And, okay, so it's been a few billion years and they might not anymore. But they might still! And…it just seems like it might hurt, is all," Martha told him.

The Doctor stared at her for three full seconds before he burst out laughing. After a moment Martha joined in.

"Martha Jones," the Doctor grinned, wiping tears of mirth from his eyes, "I'm going to try very hard not to speculate on Brannigan and Valerie's relationship ever again, and instead ask you, how is it that you learned about cat-penises?"

Martha blushed even darker and mumbled something about being a medical student.

"A medical student studying the reproductive systems of cats?" the Doctor asked.

"I think I'm going to make some tea," Martha suddenly said, headed off into the TARDIS.

"Oh, come on! You can't say something like that and then not tell me! Martha!"

Martha kept going and didn't answer. The Doctor laughed even harder.