After Cas had fallen, Sam had been setting up some of Cas’ fake IDs and mentioned that he should have some kind of birth date. Dean had looked up from the paper he’d been reading and flushed slightly before murmuring that September 18th “sounds kinda nice.” The significance had not been lost on Castiel - or Sam, for that matter, whose eyes had widened slightly - but neither of them said anything. Cas had simply smiled at Dean, eyes betraying things neither of them could say.
Months have passed since that day, and now Castiel is sitting with Dean in the bunker’s kitchen, pressing kisses at the corners of his mouth and licking stray frosting off their joined fingers. Dean pulls away suddenly and Cas startles, confused.
“I, uh… I have something to show you, Cas.”
“What?” Cas trails off before realization dawns. “Wait… I thought we agreed that you wouldn’t get me anything. I have no need for any more material possessions.”
“Uhm… this one’s kind of… figurative?” Dean scratches the back of his head, not meeting Cas’ eyes and appearing incredibly flustered. “Just… Christ, Cas, just follow me.”