More research turned out to be the answer to Dean's question, and normal sized Dean was much more distracting than fledgling-sized. Odd noises were made, drawing Castiel away from the pile of books that had steadily grown, but everytime Castiel turned to look at whatever Dean was doing the noise stopped.
"Dammit - right." Indecipherable mumbling followed the short statement, than a loud thud. "Son of a bitch!" Castiel sighed and looked to where the thud had originated from, finding Dean tangled in his wings on the floor.
"Dean. Why are you on the floor?" His face went a deep shade of red that he tried miserably to hide before turning to Castiel, looking embarrassed.
"Uh, funny story..." He nervously rubbed the back of neck, wondering when it'd got so warm and when Castiel's look had gotten so intense. "Okay, not so funny actually. It doesn't matter Cas." Castiel squinted before replying.
"If you insist." He went to turn away, but Dean stopped him, the bright shade of red covering his face again.
"Cas, wait. Could you, um... I got... Help?" Dean pointed to where the wings joined to his back, and Castiel looked confused.
"Why do you need my help?"
"I..." The answer clicked before Dean could get the rest of the sentence out, and Castiel moved so he could reach the join on the hunter's back. He slowly raised his arm towards the left wing, looking at Dean for confirmation that he could touch, and gently placed his hand where the problem seemed to be. He gently scratched the area, making Dean produce a low moan as he dipped his head as a sign to let Castiel continue. Castiel didn't acknowledge the moan, too wrapped up in how soft the hunter's wings were - they reminded him of a fledgling's wings in colder months when they left heaven. He hadn't realised that he'd started to stroke along the bone until he could no longer reach from the position he was in and abruptly stepped back, clearing his throat.
"I apologise, Dean... I... They're very soft." Dean smiled lazily, looking at Castiel through hooded eyes that had a tiny glimmer of something else in there.
"Cas, it's okay. In fact, that was better than okay." He stood up, eyes open properly, the tiny glimmer gaining more strength. He turned Castiel around and began rubbing small circles on his shoulder blades where he imagined his wings would be.
"Where d'you hide your wings? Cause I know they're there somewhere." The angel didn't reply, rolling his shoulders and then Dean couldn't see. A mix of midnight blue and emerald green swam before his eyes when the light reflected off the dark that had taken Dean's vision, and then it moved, snapping him out of his staring. Dean's mouth was left hanging open as they moved and Castiel faced him instead. Worry was written all over his face, the fear that the now adult Dean wouldn't share the same enthusiasm about them as fledgling Dean.
"Did I do something wrong?" Castiel looked at his feet but shook his head, wings almost in a defensive position. "Cas?" Dean gently lifted his head up and smiled, extending his other hand so it brushed Castiel's left wing and it extended of its own accord - shocking Castiel through both it and Dean's actions.
"I apologise... My wings are not used to physical contact. The colour seems to put other angels off..."
"There's nothing wrong with them Cas. They're... They're amazing, actually." Castiel squinted when they opened out more in response to the complement, and Dean laughed. "Seems they know it more than you do." Dean felt his own open, turning quickly to see what the hell they were doing, catching Castiel's open wing with his and feeling a jolt like electricity pass between them. He jumped away, confusion covering his face as Castiel went almost as red as Dean had earlier.
"Okay - what the hell was that?" Castiel looked at his feet.
"It... Happens... When angels have a mutual attraction... To each other." Dean didn't say anything for a minute, standing rooted to the spot with his jaw hung open.
"But..." He paused to clear his throat. "But I'm not an angel Cas, it shouldn't... Can't... Why'd it happen?"
"Being Michael's true vessel must have some effect on how your wings work, and how they interact with others." Castiel's face lit up after this, the aftershock of their wing contact distracting him from any other rational thought. Dean looked puzzled, waving his hand in front of Castiel's face to try and get a response but there was nothing. He tried for a couple more minutes before giving up and poking his wing, the electricity feeling passing between them again.