I uploaded this back in February on my AO3 account so please check it out there for the full notes. I got this idea after learning that Josh Scorcher a military Brony was a Cap fan.
The Avengers Facility, the headquarters of what could now could be known as the New Avengers. Team leader Steve Rogers or Captain America was wandering about the base, things had been quiet for the moment so he had some free time to spare.
Sam was away doing some scouting; Vision was off with Wanda so he decided to check in on what was happening with James Rhodes or War Machine as he was known. He knew that he was Tony Stark's best friend. He never did have much chance to really talk with the third military man in the Avengers.
He found 'Rhodey' as Tony called him which pretty much stuck with the other Avengers, in the sitting room of the Base watching TV. He looked to what he was watching and saw it featured a cartoon Pegasus horse flying through the sky.
"Before you say anything, yes Steve the badass War Machine is a Brony. Yes, question his manliness if you will but please just let me watch..." Rhodey shouted at him looking quite annoyed.
"Brony? You say that as if I know what you are talking about and what is this about losing manliness?" Steve asked perplexed. Rhodey looked at him for a second as realisation dawn on him and he let out a laugh.
"Oh yeah, I forgot that Captain America was in ice long before the era where it was cemented that ponies were for girls. Sorry Steve, somehow I forgot how much of an old man you are." Rhodey stated as Steve crossed his arms.
"Har-de-har, would you believe that I heard all the old man jokes since I was unfrozen Rhodey so I doubt you will have anything new." Steve responded before shrugging it off. He went down and sat next to him. "So this is one of those cartoons for kids, what is it and what is this Brony?" Steve asked as Rhodey showed him the Season 1 DVD of MLP: FIM that he had on the table.
"It's what we call ourselves, grown up male fans of this cartoon called My Little Pony: Friendship is Magic. It's the latest cartoon in this franchise made to sell girls toys." Rhodey told him showing him the DVD box.
"Been wanting to try and find more hobbies in my free time, grow more accepting of modern day. You think I can join you." Steve asked as Rhodey started laughing.
"Captain America asked me if he wanted to watch ponies with me, that sentence should never have been possible but it had just been said. I'll go to the opening two parter, might as well start at the very beginning..." Rhodey said getting the DVD player remote and selected Friendship is Magic part 1.
Several episode viewings later Rhodey stopped it and faced Steve and asked "so Cap, what do you think?"
Steve laughed and said "six individuals united together to stop a world threatening menace, why does that seem appealing to me?" Steve then laid back and asked "still if only we had the Elements of Harmony to take care of Loki, Hydra and Ultron."
"Well that seems cool until you realise the Royal Guard of Equestria is pretty much useless, trust me Cap they never succeed at anything in the show. Not even when we see their Captain does he even seem competent." Rhodey remarked looking a bit angry at the idea.
"But the two Princesses are pretty much queens but the toy company thought that queens are evil?" Steve asked remembering how Rhodey explained it to him when he brought it up earlier. "Plus the most popular characters are the background ones, including the one who came about because of an error?" Steve asked and Rhodey nodded.
"I know, I mean if you are watching something you like then why get over anticipated over even a mere cameo that might not last that long?" Rhodey asked as the headquarters' janitor an elderly white haired man with glasses passed by them while sweeping the carpet.
"Amen to that Colonel Rhodes." The man shouted Rhodey giving him a salute before going on his way.
"Hopefully I can watch some more with you sometime. It seems innocent, cute and fun." Steve told Rhodey and it was there when War Machine realised he may have turned Captain America into a Brony.
It was about a month later when Rhodey saw that Steve had now decorated his room with posters and plush toys. "I have created a monster..." Rhodey muttered under his breath.