It wasn’t Batgirl but Robin who pulled the old send your boss his father’s costume to drudge up old memories so that he can get back to fighting for justice ruse. What a prankster, that kid.
Now for 2 Truths/1 Lie. The year is 1981:
Batman and The Hulk crossed over into each other’s world in DC Special Series 27. The Joker at first used The Hulk to go after Batman but they eventually teamed up in the end to fight the reality-warping Shaper of Worlds.
After Superman and Batman, Green Lantern got his three issue miniseries called Tales of the Green Lantern Corps. It retold Hal’s origin but also introduced us to Arisia, Hal’s sector neighbor, and Nekron, who would go on to mastermind Blackest Night.
Superman and Spider-Man also teamed up this year (although it was the 2nd time they did so) but they weren’t the only heroes involved. Namor stumbled into Aquaman’s ocean and at first didn’t realize he wasn’t in his home world. Due to misunderstandings the two fought until they realized their mistake (with the help of Supes and Spidy) and focused on getting Namor and Spidy back home.