We're here for the book
Just after their first meeting before anything can happen between Nightwing and Batman a problem crops up. There are a bunch of Jokerz right there and a creature that looks like it is made from the nightmares of Gotham herself. It stands back but gibbers something at the apparent leader of this group of Jokerz.

"Yeah, yeah I hear ya. Hold yer horses," he slicks back his hair and offers both heroes a grin. "My pal here has asked us ta get something from ya Bats. We want the diary of Randolph Carter. Hand it over or we'll take it from ya. Either way we win."

Twenty Jokerz, a Cthulu spawn, and two of Gotham's finest. This looks good.