Phil Asks Agent Barton to give him a report of what he sees going on in a research center. However most assume they may have a bigger back story.
After Coulson is brought back from the dead, none of the Avengers are aware. They all believe he is dead, including Clint.
It's expressed in the fandom that Phil Coulson was Agent Barton and Agent Romanoff's handler. This means that Phil and Clint would have known each other a lot more than the films let on.
The fandom took off more in anticipation for the first Avengers film.
- “Clint/Coulson first started as a ship on the Thor kinkmeme, probably because it was the only viable slash option that a) wasn't incest and b) didn't break up a canon couple. The foundation for the pairing might have been thirty seconds long but it also followed a well-loved tradition of snarky/deadpan pairings, so there was an easy setup there. Also, they were both blank characters with little backstory in the MCU who had no visible love interests, which lured in fans who are otherwise hesitant to write for comic book movies. Thanks to a couple good prompts and fills, C/C gained a modest but loyal following. Then the Avengers came out, which provided a huge blow up in MCU fic in general, but also a) gave Coulson more characterization and b) resulted in people picking up the Fraction Hawkeye comics in an attempt to characterize Clint better. Upon the realization that Coulson was a secret dork and Clint might be a secret failboat, plus the fact that neither of them had an onscreen love interest, the pairing took off. It also helped that some of the early fics were both longer and really, really good. People would click on the pairing tag out of curiosity, and find good fic--of course it got big.”