AN: Just a little something that popped into my mind. Maybe the Doctor wears the fez now because he didn't want to once in the past. And maybe it was Susan who was asking him to.
In the early days, before the Doctor had humans along, and it was just Susan and himself, he didn't usually indulge himself in the idiosyncrasies of wherever they landed. He preferred to watch from a distance as a spectator, but not have to get involved with whatever mishap they came across. Besides, getting involved in history was risky and he didn't want to change anything that ought not to be changed.
His granddaughter was an entirely different story though. She wanted to dive head first into the culture of wherever they were; see the sights, meet the people, try the food, and pick up a souvenir or two. He constantly had to remind her to be careful who she talked to and what she was doing. They didn't want to draw attention to themselves, since they weren't supposed to be there in the first place. She would nod in agreement and the moment his back was turned, she would be off chatting up the locals or sampling a snack at a nearby market.
But more than anything, she loved collecting souvenirs. The TARDIS was littered with bits and bobs from all different times and planets. Clothing from every place they visited soon filled the wardrobe room whenever Susan found something else she wanted to wear. The Doctor would usually shake his head at her actions, but let her collect her things. It livened up the ship and it kept her happy.
Despite whatever the Doctor claimed, he didn't have much control over where the ship took them, and for whatever reason she tended to take them back to the planet Earth quite often. As a result, the two of them became well versed in the history of the planet. Susan was delighted, since she had grown to love it and the people who lived there. The Doctor tolerated the humans but didn't regard them very highly compared to other species they had encountered in their travels.
On one particular trip that had resulted in them landing some time in Earth's history again, Susan stole off on her own. This did not go unnoticed by the Doctor for very long and he was rather gruff with her when she returned, mostly to cover up how worried he had been. She had run up to him, pink-cheeked and slightly out of breath, with a red cap perched on top of her dark hair. A similar one was clutched in her hands.
"And where have you been child, hmm?" her grandfather demanded. "I told you about wandering off!"
"I was just down the street, Grandfather," Susan protested. "I met some lovely people – and they gave me these!" She offered the hat to him.
"And what is this then?" he asked, peering closely at it.
"It's called a fez," she explained. "It's a type of hat they wear here –"
"Well it looks ridiculous," he huffed. "Besides, what do I need with that in the TARDIS? Completely unnecessary. Now, come along child, we are leaving. I don't want you wandering off again."
Dejectedly, Susan followed her grandfather back to where they had parked the ship and later stowed the hat meant for him somewhere deep in the wardrobe room. Her own was kept in her room, but she didn't get the chance to wear it again.
A regeneration later, Susan was gone and the Doctor had developed quite the fondness for hats. He had made it a habit to collect as many as he could from wherever they landed. He was poking around the in wardrobe room one day when his hand brushed against red velvet that was hidden between a heavy traveling cloak and a pair of fluffy slippers. He pulled it out and was surprised to see that Susan had kept it all along. Turning it around in his hands, he could clearly envision it being clutched in small hands that held it out to him.
He couldn't wear it now; the memory was still too strong and he wasn't ready to dwell on the memories of his beloved granddaughter. Instead, he tucked it away in a safe place in the TARDIS as a memento and a promise that he would give new things a try in the future.
It would be quite a few regenerations later when he would end up in a creepy basement and he came upon a fez by chance. He put it on as a joke to try and lighten the mood for his companion. It took him a moment before he remembered the neglected gift from his granddaughter and he was surprised to find himself still saddened that he hadn't given it a chance the first time. These days, he would have done anything to see her bright smile again. He gave himself a mental shake and focused on the current situation again.
The Time War changed everything. He was miserable for so long but his human companions (it was humans, always those humans) helped him through. The young, blonde shop girl (who indirectly shared a name with someone from very long ago) was at his side, with a quick smile and cheerful conversation. He learned to laugh, love, and open himself up to others again. The guilt still weighed down on him, but he put on a smile and was able to enjoy life and adventures again.
His latest regeneration (so young for someone so old) was good at cheerful. He ran around, indulging himself with childish whims. And when he found a fez again, he plopped it on his head without thought. He had made a promise to himself that he would not be a bystander. He would see the sights, meet the people, try the food, and pick up a souvenir or two. True, his souvenirs tended to be companions but they were the best to learn from. Although he didn't really think of his family now (not explicitly at least; they were there in his mind, hidden from thought, but they lived in his hearts) they influenced his decisions and actions. And so instead of scowling at the silly-looking hat like he had once upon a time, he gladly wore it. As a testament to his granddaughter, to hope, to wanting to just be happy and to the fact that it didn't really matter why; he could wear a fez if he wanted to.
Feedback is much appreciated.
