"Hey, Doc, where's Rose?' Jack asked as he came through the door of the Tardis.
The Doctor had his back to the door and didn't seem to have heard, so Jack gently poked him in the side. He gave a very un-doctor like squawk and sprang around, glaring at Jack.
"You're ticklish." Jack said with a grin.
"I am not." the Doctor said with a huff, "You startled me, that's all."
"Are so." Jack said poking him again. The Doctor squirmed away. "You." poke. "Are." poke."Ticklish." poke.
"Stop it, Jack." the Doctor growled.
Jack grinned and poked again.
"I mean it, Jack," he warned, "stop tickling me."
"Or you'll do what?' Jack ask, poking again.
The Doctor lunged forward faster than Jack expected and grabbed Jack's wrists in one hand.
"Are you ticklish, Jacky-boy?" he asked in a soft, menacing voice. "Shall we find out."
He ran his free hand along Jack's side. Jack twitched. He wiggled his fingers along Jack's ribs and Jack squeaked and tried to squirm away, but the Doctor was too strong, he couldn't get free, so he did the only thing he could think of and threw himself against the Doctor, knocking him to the floor. Unfortunately he didn't let go of Jack's hands as he fell, so Jack was pulled down on top of him. Jack yanked his hands free and attacked, poking the Doctor with both hands as fast as he could. The Doctor tried to block the attack with one arm while launching his own assault. They wrestled and tickled and rolled across the console room floor, squeaking and cursing, each trying to gain the upper hand. They rolled down the ramp and came to a halt at Rose's feet as she stood just inside the door.
" Why are you two ticking each other?" she asked.
The two men looked at each other and shrugged.
"Men," Rose said, shaking her head, "leave them alone and they turn into little boys."
Jack looked at the Doctor and wiggled his fingers. The Doctor grinned. On a silent count of three, the two of them jumped to their feet and grabbed for Rose.
" Oh no you don't!"she squealed, dodging out of their reach.
She ran with the two of them right behind her, laughing as they chased her through the Tardis.