There's something to be said about Steve Rogers doing girl-pushups.
And then there are those jumping jacks he does.
It's even funnier seeing Chris Evans do them behind the scenes!
When presented the challenge of grabbing a flag on a very high flagpole (the reward is a jeep ride back to base with Carter), something no soldier has managed in over 17 years. The other soldiers scramble all over each other trying to scale the pole, but (pre-supersoldier) Rogers outsmarts his stronger squadmates by simply detaching the pole's anchor bolts and letting it fall over, rather than trying to scale it. The soldiers' and drill instructor's faces when he pulls it off are priceless.
Peggy is definitely impressed and amused.
Steve not knowing what "fondue" is, and assuming it is something sexual.
When they're in Brooklyn, Steve lists off all the places he got beat up as they drive by them, solidifying his status as The Woobie for many viewers.
Gotta love the part when some kids in the audience notice the Hitler impersonator sneaking onto the stage, and say things like, "There he is, Cap! Look Behind You!"
When Cap has rescued the prisoners and tells them to clear out while he searches for Bucky, we get this exchange:
Soldier: You sure you know what you're doing? Steve: Don't worry. I've punched out Adolf Hitler over 200 times.
Before the procedure starts, we have everyone in the lab stopping dead in their trackswhen they see Steve for the first time. Peggy's reaction is just a resigned sigh and a "let's just get this over with" expression.
However, after the procedure she's Not So Stoic. She's as gobsmacked as everyone else, and actually sneaks a feel of the dazed and newly transformed Rogers, before pulling back.
Phillips: What about cyanide? Does that give you the rumbly tummy, too?
And then Phillips promptly starts eating the steak himself.
On a related note, Phillips' later description of Zola as "my new best friend" when he's debriefing the others.
Philips giving a speech to the new recruits, and as he says "We are going to win this war because we have the best men", he suddenly pauses and stumbles over the last word when he lays eyes on Rogers, a foot shorter than the other troops and still skinny and scrawny. He then ab-libs "And because they are gonna get better... much better..."
Steve reuniting with BFF Bucky Barnes, who notes his friend's transformation.
When the Skull and Zola are fleeing from their exploding lab, Zola points out that the Skull's escape Triebfluegel only seats one. The Skull responds by calmly turning to Zola and handing him the keys to his car.
There's actually a moment where you think that the Skull is going to just leave Zola behind, but then...
When Red Skull is being chewed out by the SS officers, he makes a hysterical 'One Two Three' motion with his fingers, pointing at the Nazis, just so he can adjust his death ray properly. All without pausing in his speech.
And when one of them starts to yell at him and declares he will be punished by Hitler for his treachery, Skull raises his eyebrows and makes a head motion to the effect of "oh really?" Then when he begins firing, one of them dodges a couple shots and he scowls, like he's thinking "Oh come on!". Finally, when he connects with the next shot, he gives a little nod, as if thinking "There that's better."