The Doctor was running in front of Donna and Jenny, all three running to find Martha, and not get shot by Cobb's underlings. After a while, Donna was noticing that they were starting to almost keep up with him, which didn't usually happen. She knew it was important for the Doctor to be at the front, since he knew more than her about, well, everything, especially how to avoid being shot by human clone soldiers from space. So she slowed down to maintain her and Jenny's position behind him. It was while focusing on her pace, that Donna noticed how the Doctor was running. He usually did kick his legs about like a jaguar, but this time, his legs were not only more stable, but clenched together, whenever they were off the ground. He kind of looked like he was doing yoga while running. Nonetheless, it was highly unusual.
"Does he always run like that?" Jenny asked, equally curious.
"As far as I'm aware, never," Donna replied.
"So you don't know why he's doing that now?" she asked.
"No clue" Donna confirmed.
They came to a stop at yet another multi-numbered sign. While the Doctor studied it, he once again kept his legs shut together, his face obviously frowning.
"Doctor? Are you alright?" Donna asked, concerned.
His frown changed from constrained to nervous. His excessive need for the loo was difficult enough to deal with, without having to tell his companion, when there wasn't anything either of them could do about at that moment.
"Yes, just a bit...tired," The Doctor lied, fully aware that he was rarely tired during adventures, and never, in the presence of a companion. His Gallifreyan biology ensured that.
Donna let the matter rest, despite not believing him in the slightest. So far, she had never seen anything exhaust the Doctor, so him being tired now, didn't sound plausible in the slightest. There was definitely something wrong with him though. She resolved to ask Martha. She was a Doctor. Whatever the Doctor was hiding, she'd probably seen it before.
The Doctor found the Source in what looked a lot like the botanical gardens. It was then, that Martha reappeared, followed by a small group of Hath. It was a sweet reunion. Apparently, Martha had managed to help a major officer by re-adjusting his shoulder, WHILE in a potentially dangerously radioactive area.
It was while hugging the Doctor that Martha realized something was wrong with the Doctor. His muscles felt really tense in the hug, like he was keeping something tight. She dismissed it as him simply still being uncomfortable with having a daughter, not to mention the way he got her.
Donna walked over to Martha and quietly asked: "You haven't noticed something odd about the Doctor, have you?"
"Yes, I have. He was really tense when I hugged him. What did you see?" Martha replied.
"He was running really weird, with his legs clenched together, also when standing still. He was frowning, looked worried," Donna explained.
It was her description of the Doctor's legs that made Martha instantly aware of what was wrong with him. She shook her head and rolled her eyes in mild, exasperated disbelief. After all her reminders…
"I can see why he would be.." Martha remarked dryly.
"You've seen it before then?" Donna asked.
"Sort of. Similar enough. I really thought it wouldn't repeat itself! 'specially considering what I told him."
"So, what's wrong with him?" Donna asked.
"He needs the loo. Quite badly, probably, considering how tense he is." Martha clarified. Donna nodded in understanding.
"So, this has happened before then?"
"Once. I told him not to let his pride hurt his bladder, even reminded him to go several times before most of our adventures, and now, the second I leave, he goes right back to old habits!.." Martha exclaimed, scoffing. Donna nodded in agreement, albeit with zero annoyance, but lots of sympathy.
The two women decided to look for a bathroom for the Doctor. One of the Hath pointed out where one was.
Donna walked over to the Doctor, who, unbeknownst to him, was squirming while talking to General Cobb.
"Martha told me what's wrong," Donna told him.
The Doctor's eyes grew wide. He blushed, and looked down at the ground awkwardly.
"Has she now.." he replied, giving a half-hearted attempt at denial.
"Yes. And it's alright," Donna reassured him by stroking his shoulder.
"We asked around," she explained, beckoning him to follow her.
They stopped in front of a door with a toilet symbol.
"Thanks, Donna. And Martha, too," the Doctor remarked gratefully, ceasing his embarrassment.
"Next time, tell me. It's completely natural, there's no need to hide it. It's no problem," Donna reminded him kindly.
"I'll try. Be right back," he replied, with a half-confident smirk to the right, before walking into the bathroom.
Once situated, the Doctor considered what Donna had told him to do. He did trust Donna, he felt even more comfortable around her, than with Martha, so the fact that Martha was a Doctor and Donna wasn't, wasn't a problem. Despite his general shyness, the Doctor resolved to at least try, after all, he had a bigger vocabulary than most humans and other species, probably. So I can probably find some subtle way of hinting to her, when I need to go, The Doctor thought, with confidence.
He walked out with a big relieved smile on his face, to the sight of both Donna and Martha.
"Better?" Martha asked.
"Much better. And Donna talked to me, won't happen again", the Doctor replied, raising his eyebrows in disdain, and for emphasis.
"Good," Martha said with a chuckle, already forgiving him.
The had a nice chat about "the prison cell" incident as they walked back to the TARDIS. The End.
Ok, I'm running out of ideas. If you have any prompts relating to the Doctor and Donna(no more Martha), please send them to me in a PM. Thank you so much!