A/N: I don't really know if the Doctor would ever go and leave Donna a present, but for the sake of this story, he does.
Amy, quite by accident, stumbles across a tiny little bathroom tucked away in the back of the TARDIS. Well she thinks it's the back, but one can never really tell. She wasn't, in God's honest truth, even looking for a bathroom, but now she's here she might as well take a look around. There's so much he doesn't tell her so she figures she might as well try and find it out by herself.
Although, she decides quite quickly, this doesn't look much like his sort of bathroom. His hair is bountiful, indeed, but Amy refuses to believe he's a vanilla and peaches kind of guy. Various mascaras and make up brushes are discarded around the sink; a painful reminder that she wasn't his one and only. But then he wasn't hers, so she couldn't really complain. She examines each one at length, as if she was trying to gauge what sort of woman he'd had with him before but mascara's weren't much of a giveaway. A slight tremor causes the room to shake (Amy doesn't even flinch – it's somewhat of a constant when you live inside the TARDIS.) As it shakes the tinkling of little glass bottles averts Amy's attention. A dozen – maybe more – little perfume bottles stand collected on a shelf in the corner. Some are ones she recognises from Earth, most of which are half empty and covered in dust. But some are unfamiliar and as she picks up a small lilac bottle from the back, she can't help but put some on. It's a powerful scent that fills the room but it's pleasant, so she applies a few more squirts and then replaces the bottle.
Smoothing down her hair as she peers into the mirror, she smiles and leaves, finding her way back to the dining room in which Rory and the Doctor sit, both in deep conversation. Neither one hears her enter, it's only when the perfume reaches the sniffing distance of the Doctor that he discovers they've been joined.
"Donna?"
"Amy," she corrects him, ruffling his hair as if his brain's come loose.
"You smell different." He stands up and places his nose onto her neck, a sight that puzzles Rory slightly. "Are you wearing a new perfume?"
"Oh this? It's old, real old. Rory got it for me when I was fifteen. Didn't you Rory?" This was the one time she was asking him to lie (apart from when she'd accidentally stolen a pug-beetle) and she needed him not to let her down.
"Oh yes. So I did." If his voice was any more high-pitched, only Rolo could have heard him. The Doctor eyes them both warily and eventually Amy gives in.
"I found it, alright? In a little bathroom. The bottle looked pretty." She dares a look at his face and he's not angry, more absent.
"That was Donna's perfume," he informs Amy, a wistful look taking over. He remembers everything about his former companions, naturally, but perfume was one factor he could attribute to Donna specifically. Rose was too youthful and adventurous to wear perfume; Martha was always lending money to one family member or another, meaning her purchases were always waylaid but Donna, Donna liked her perfume and he would always remember. "She bought it on Pentium from a lizard who gave us a ride to the Pyramids of Dulu."
Rory never knows when he's telling the truth, but then again, living for 900 years would mean an awful lot of travelling. The Doctor suddenly becomes thoughtful and wanders out the room, muttering under his breath. He returns fifteen minutes later, the bottle in his hand and he scrawls out a little message and attaches it to the lid.
"Rory, Amy, mind if we take a detour?" He doesn't wait for their answers because he's going to do it anyway. This is his home as well as his transport and frankly, they either like it or leave. "Next stop, the residence of all things Noble."