The Doctor and Peri had been heading back to the TARDIS after yet another adventure where the Doctor had insulted Peri just about any and every way he could, and Peri took it like always because frankly, who would turn down the chance to travel anywhere and everywhere in Time and Space, even if the driver was a complete ass? At least he was taking his homicidal urges out on unpleasant people like the Daleks, the Cybermen, the Androgums, and that guy at the hotdog stand who put lettuce on his hotdog rather than on her.
When they were less than two feet away from the Police Box that the Doctor called home, there was the sound of another TARDIS materializing nearby. Turning to look, in case it was the Master up to his usual tricks again, Peri and the Doctor watched as a porta-potty on which someone had sprayed the words "Party Wagon" in Gallifreyan materialized less than a block away. A minute later, the door opened and a brunet of average height tumbled out.
"I picked a bad week to stop sniffing glue." the young man said from his spot on the pavement, and there was a chorus of "Airplane" from within the TARDIS he'd fallen out of.
As the Doctor and Peri watched, a rather familiar looking young man in an Army Lieutenant's uniform emerged from the Porta-TARDIS and said "Come on Thete, up you get." as he helped the young Time Lord up off the ground.
A Couple of Decades Earlier/Centuries Later/Whatever:
Colonel Lethbridge-Stewart knew that his plan to risk virtually the all of his remaining men to retrieve this Doctor fellow's police box seemed insane, and that he probably should've shot the Doctor considering the fact that several statements made seemed to indicate that he'd been working with whatever the hell was terrorizing London. But, the man seemed trustworthy and very familiar for some reason, and if this police box was anything like Theta Sigma's old Party Wagon...
It was a risk he would have to take. It was a risk he took, and it was a risk that had cost a number of lives because the thing that had taken over Staff Sergeant Arnold had placed a Yeti homing device on him without him realizing.
After the mess with the Great Intelligence was over, he had turned to ask the Doctor if he knew Thete, but the little man and his friends were gone. By the time he reached Covent Garden Station, there was absolutely no sign of a police box, or a box of any sort.
Back with the Doctor and Peri:
As Peri and the Doctor watched, the young Lieutenant Lethbridge-Stewart, a dark-haired man, a brunet man in a long coat that had a vortex manipulator strapped to his wrist for some strange reason, a red-haired woman, and a woman who looked to be in her forties with curly blonde hair picked "Thete" up and carried him into the nearest pub, laughing the entire time as "Thete" spoke in movie quotes which one or more of them would quickly identify.
"So, that's what happened to the seven years after I graduated the Academy." the Doctor said.