Jack's smile widens into pure delight and there's that ever-present joy when he walks into the life of his Doctor. "I knew it was you! It's the eyebrows." Mostly the eyebrows when they do the furrowing or the raising of them. Even the new female version had that going.

It being Jack, he immediately closes the space between them and wraps the Doctor into a hug whether he likes it or not. A big hearty one too. He may look slightly older than the last time he saw him, it's very hard to tell with Jack since he ages so slowly, but there was a wrinkle or two around his eyes that have a hundred years or so of backstory.

No matter how many versions he meets of the Doctor, he always feels like being in his/her/their presence is a relief, a comfort. Jack may outlive everyone around him, but he always manages to run into his favorite alien sooner or later.

"Okay so quick time check." He would keep hugging him if he could. "You wouldn't happen to have been a pretty blonde woman before this would you?"