For the God of Mischief's Birthday (слэш)

When JARVIS's systems are mysteriously overridden, the Avengers get a nasty surprise. Then they get another one--in the shape of the God of Mischief.
Loki would just like to point out that none of this is his fault. After all, he was perfectly fine reacquainting himself with Frigga in Valhalla. But as long as he's back... Well, let it not be said that he cannot take advantage of an opportunity when he sees one. And Tony Stark is definitely an opportunity--and so much more.