Tony on Tumblr
I read a long time ago a multi chapter fanfic (the last chapter was chapter 4 I think but maybe they wrote more) where the Avengers got themselves an assistant (or liaison? Something like that). In there I remember that the assistant found out that Tony sings in his workshop and convinced Tony to let them record him and post online. I also remember that Tony found out about Tumblr and was convinced they were his people and/or trolled them. This was on ao3.