For the most part, I decided early on not to create birthdays for pups who don't have canon birthdays. So their deeper feelings tend not to emerge. However...

Charlie the orphan doesn't know when his birthday was. And has no desire to create a fake birthday based on when he was found. Birthdays are simply for other people.

Kirk obviously celebrates his birthday (March 22, based on Shatner's birthday), since we had that memorable scene from Wrath of Khan where Jim felt old. Some years he still likes to celebrate, others he doesn't. I should probably give him a cake this year as time runs out on him.

Knox is private about his. He passed 40 without a word to anyone but Rapunzel in 2011, and is maybe a little touchy about age since his girlfriend is virtually immortal. But he's never made a big deal of the day. Seems silly to him.

Gibbs comes from a time when birthdays were not a big deal, and people didn't always know the date. Or their ages.

Howard usually lets someone throw a small party for him, but this is more a social obligation kind of thing.

And Cy tries not to let the team know when his birthday since their parties are likely to go all wrong.