When Hermione stumbles in from Ginny's bachelorette party, it's already four in the morning. He's fast asleep, already, so he doesn't even register her plopping into the bed with him, still fully clothed. She falls asleep almost instantly, tired and more than a little bit drunk and doesn't even register she's in the wrong bed.
Fred wakes up choking on a mouthful of hair, with a pointy elbow digging into his ribs, and a high heeled shoe lodged somewhere near his spine. Completely and thoroughly confused, he still moves slowly away from the hair monster.
Sitting upright, he can finally recognize his bed companion as none other as Hermione Granger. That is when he squeals.
After the initial squeal, Fred stills, looking at Hermione carefully and waiting for the inevitable attack which, well, doesn't happen. What does, however, happen is Hermione turning to lay on her back, her hair spread over his pillow, face completely serene. And Fred's breath catches in his throat as he watches her with utmost attention, memorizing everything about the moment; because he knows, this is a once in a lifetime opportunity and he's never going to have her in his bed again.
So he lowers himself softly back next to her and keeps looking, a shy smile on his face. And in this moment, he could swear, she's sparkling. He doesn't even notice falling back asleep but he does so with a smile on his face.
When Hermione wakes up a few hours later, she's enveloped in Fred's arms and it makes even the raging hangover she has feel like bliss. Still, she shimmies out of the bed (and his arms), takes off the one shoe she still had on, and tiptoes towards Ginny's room to clean up. At the door, she stops, just for a moment, glances at Fred and sighs.
He wakes up for the second time to an empty bed and cold sheets and he can't find any trace of her so he assumes that it was all a very elaborate, real-feeling dream. It immediately dampens his mood.
Still, he gets up, showers, and then promptly marches downstairs to eat breakfast with his sister and Hermione. He looks at his reflection while passing a window and grins, feeling exceptionally dashing this morning.
In the kitchen, Hermione is just as sparkling as she was in his dream so he sighs before helping himself to a healthy portion of eggs. When Ginny arrives, he's already stuffing his mouth full of them.
Ginny comes down for breakfast after her Bachelorette party and sees her brother and her best friend both covered in glitter, both stuffing their faces in silence. With a mischievous grin, she asks:
"So, Hermione, where did you sleep last night?"
At Hermione's blush, she keeps on prodding.
"Fred, do you by any chance know where Hermione spent the night?"
As her brother's ears turn red, she goes in for the kill.
"Fred, you realize you're covered in body glitter?"
At this, Hermione starts coughing while Fred just looks at her, baffled.
"Covered in body what?"
"Body glitter. That's why you're sparkling."
"I'm sparkling? She's sparkling!"
He yells out, waving his hand in Hermione's general direction.
"Yes, that's because she put on body glitter last night. It doesn't really wash off. However, it does rub off." Pause. Then: "Is there something you two want to tell me."
At which point Hermione sharply stands up, knocking down her own chair, her face red from her coughing fit and her hair wild, and yells out: "Oh, relax, it's biodegradable!" And runs upstairs.