This takes place between chapters 66 and 67 of De-aged. This is it posted in it's entirety.

Jack entered the sunroom where the Doctor was meditating. Said alien was sitting quietly on the floor surrounded by potted plants he had clearly moved into a circle around him. Jack wondered how the Brigadier would feel about the dirt tracks across the floor or about having to rearrange all the pots when the Doctor decided he was done.

Jack was wondering what he should do and how angry the Doctor would be if he disturbed him, when the Time Lord's eyes snapped open. They found Jack's immediately. "I've got it," he said. He stood up fluidly and strode out of the room, a very confused Jack trailing behind.

"Got what?" Jack asked, as the Doctor headed for the kitchen. He was ignored.

The Bridgadier was still in the kitchen, debating whether it was time to start lunch when the Doctor and Jack entered the room. "What's going on?" he asked.

"Got me," Jack said, staring at the Doctor.

The Doctor was rummaging through the refrigerator. "No. No. No," he said, shoving random food items out of the way. "Aha." He pulled out a gallon of milk. "And..." he pulled out some orange juice. "Good, good." Jack stared at the milk and orange juice with trepidation. The Doctor was still searching. "Last thing... oh, yes, this should work lovely." He pulled out a half-finished tin of anchovies .
Jack turned to the Brigadier. "Why do you have that in your fridge?"
The Brigadier frowned at Jack. "I like anchovies on my pizza. That's a crime now?" he asked.
"It should be," Jack muttered. "Doctor, what are you doing?!" The Doctor had poured the milk and orange juice into a glass together and was now enthusiastically chopping up the anchovies with a large chef's knife.

The Doctor ignored Jack and instead scraped his anchovies, now a coarse paste, into the curddling milk/orange juice mixture. Pulling out his wand (that he was apparently keeping in his sleeve), he mixed the concoction a few times with it. When done, he pulled it out, wiped it off on his sleeve, then tapped the glass twice with it. "Finite incatatum," he said. The contents turned from a creamy orange to a sickly brown and started emitting a horrific odor. The Doctor then split the mixture into two glasses and gave one to Jack. "Drink up," he said, and, putting actions to words, started chugging his own glass.

Jack shot a desperate look of panic at the Brigadier, who just shrugged and gestured for Jack to get on with it. Jack swallowed hard and started cautiously drinking the foul liquid. It tasted as bad as it looked, and Jack gagged and started coughing. The Doctor, still working on his own potion, gestured for Jack to get a move on. Jack grit his teeth, held his nose, and started pouring the liquid down his throat.

By the time the Doctor finished, Jack had caught up, and they put down their glasses together. "Doctor, I trusted you, can you explain what-" Jack's demands for an explanation ceased as, with a loud pop, he and the Doctor both shot up, growing to full size.

"There we go, lovely," the Doctor said. "We're done." He smiled at the Brigadier. "Thank you for your hospitality." He turned to Jack. "Ready for our next adventure?"

The end.

A/N: And thus concludes De-Aged after... what, 3, 4 years? I think I'll take a break from writing fanfiction now...

I kid, I kid. April fools, y'all.
In all seriousness, I just finished a month of 78 hour work weeks with 40+ minute commutes each way. Today, I started a week of 12 hour days. I'm currently typing this at a nurse's station, hoping nobody looks over my shoulder. For the first time, I will not make the day I said I would. I was going to give you warning but thought an April fool's joke would be more fun. I will have a real chapter up before the end of this month, but I'm not sure when. Sorry! See you soon, B