Sebastian Stan is ruining my life...

(Bonus cuteness if you're imagining poor Steve left behind, trying to explain that sometimes people get so happy and love something so much that they can't help but cry, when poor Peanut thinks they made Bucky sad instead)

Bucky feeling Peanut move for the first time... the circumstances he's in when it happens, his initial response, his response when he actually figures out what the hell it is... it'll all be pretty classic (when we finally effing get there)

He won't actually /really/ freak out until he's actually in labour... up until that point he'll just be so over it and anxious to get the show on the road that he won't freak out about it. And even at the beginning, he'll be glad that there's an end in sight. At least, until active labor hits. THEN the proper panic will set in.

... great?

He'll be very, very worried once the flip comes that he won't be able to be the parent that Peanut deserves, between his circumstances and his personal history and how hard he will have worked by that point to distance himself from the baby... but ultimately he won't have anything to worry about.

It will depend on the baby, but all will definitely respond to external stimuli. The amount that they respond and how long it takes for them to calm down will really be the main thing that differs by baby...

No fights, no, although Steve will get to feel some of the hormonal wrath that Bucky had to deal with on his own this time around with the later pregnancies...

Yeah... its going to be a really annoying side effect that he hadn't considered going into it. When Nat buys him his first tin of coconut butter he'll be pretty miffed, and even more so when it comes to be his most valuable possession.

At first it will be getting really riled up in the middle of the night and waking him up or keeping him awake, but overall it will definitely be stretching into his diaphragm.

No… in large part because by the time Peanut starts becoming really interactive, he’s going to start failing really badly at distancing himself from the baby. Once the decision is made to co-parent, Bucky is already going to be pretty head-over-heels for Peanut

Yeah, there will be a few… the first one is actually coming up in a couple of chapters. When they happen at first they will be annoying/embarrassing, for Bucky especially (obviously), although as time goes on they’ll both get to the point where they can laugh about it/look forward to telling/embarrassing Peanut about it someday.