Based on this prompt from geodude96 on Tumblr: They're pulling an all-nighter at the foundry (or are there late, in any case). Felicity has fallen asleep, but suddenly wakes up terrified because she had a nightmare about kangaroos (remember she said she was afraid of them?) and Oliver is there to comfort her. Bonus points for Diggle observing and quietly shipping them.
It's not uncommon for them to return from a mission and find Felicity asleep at her desk. Oliver always tells her she's free to leave once the work is done, but she's never once taken him up on the offer. So, when he and Diggle come back in the wee hours of the night after a long, fruitless stakeout and find her with her head resting on her crossed arms, fast asleep, Oliver's not surprised. It makes him smile even.
"You go ahead and change first," Oliver whispers to Diggle. "I'll wake her up." The other man nods and tiptoes toward the back room while Oliver silently approaches Felicity.
Typically, her sleep seems so peaceful that he can't help but envy her, but, tonight, something is different. He's well acquainted with what having a nightmare looks like and when he approaches her desk, he knows Felicity is in the grip of one: her hands are clenched, her forehead is creased in worry and covered in a light sheen of sweat, her indistinct murmurings are permeated with the unmistakable sound of fear.
"Felicity," he says softly, but it has no effect. "Felicity," he repeats more loudly, leaning down and resting a hand on her shoulder. She still doesn't wake and he has to shake her lightly, her words becoming more distinct as he does.
"Not in the pouch!" she yells, startling herself awake and causing Oliver to step back in surprise.
"Hey, it's OK," Oliver says comfortingly as she looks around wildly. "You're alright."
"Oliver," she sighs and relaxes, finally realizing where she is.
"What were you dreaming about?" he asks, squinting in confusion. "You said something about a pouch?"
"Oh," Felicity says and blushes. "Um, kangaroos?" she says and grimaces.
"Kangaroos," Oliver repeats because that is pretty much the last thing he ever expected her to say.
"Uh, yeah, I kinda have a phobia," she says, but seems to understand from the skeptical look on Oliver's face that that doesn't quite explain it. "This is actually pretty common for me," she says with a resigned sigh. "Usually, I'm in a desert landscape, totally alone, when a giant kangaroo hops up out of nowhere and starts chasing me. Usually, I wake up before it catches me, but I guess when you tried to wake me up, the contact changed the dream and this time it caught me and picked me up and it was gonna put me in that dark, gross pouch and...Oliver, don't you dare laugh at me."
He snorts and then covers his mouth with his hand. "I'm sorry," he says and collects himself. "But it's a kangaroo, Felicity."
"Do you even know anything about them?" she asks defensively and then goes on to list kangaroo-related facts, counting them off on her fingers. "The groups they travel in are called 'mobs,' they box and kick each other for fun basically, they can hop like 40 miles an hour." She doesn't get farther than that because her diatribe has the opposite of her desired effect and Oliver is practically shaking with laughter.
"Stop it," she says, sounding hurt. She tries to slap his arm, but he easily dodges the blow. "Hey, not all of us have nightmares about the deserted islands we were trapped on," she grumbles and it immediately extinguishes Oliver's mirth, the reminder of the images that keep him awake most nights and the fact that she somehow knows about them stinging.
"Oh, God, Oliver, I didn't mean..." she starts and stands. She fidgets a bit and when she speaks, she waves her hands around awkwardly, the words coming in a rush. "You were asleep on the plane back from Russia and you started talking in your sleep about Slade and Shado and Sara. And then you started getting louder and all sweaty so I tried to wake you up, but then you kind of swung at me." Oliver flinches at the thought and tries to draw away again, but Felicity sets a comforting hand on his arm. "It's fine, I probably should have realized that was a bad idea," she says softly.
"Eventually, I just sat down next to you and rubbed your head. That's how my grandmother used to calm me down after a nightmare," she explains, her voice small and sad as she automatically reaches up to demonstrate. She freezes when her fingers first tangle in his hair and looks at him apologetically–like she's crossed a line–but then Oliver shuts his eyes and leans into her touch and she moves her hand again, sending a tingle down his spine as her nails scrape against his scalp. Her hand comes to rest on the side of his neck and Oliver opens his eyes again and smiles at her.
"Thank you," he says sincerely and places a hand on her shoulder, even more touched by what she did because he remembers how furious Felicity was with him then.
"You're welcome," she says just above a whisper.
It's then that Diggle walks back into the room, but when he sees the way his partners are standing, he stops and retreats to give them a few more moments and wonders for the thousandth time when they'll figure it out already.