Obviously, huge Suicide Squad spoilers here if you want to read on so here's a Batman with a bomb to prevent you reading anything accidentally. If you want to see more then scroll on by.
Okay then. So as noted on Birthsmoviesdeath.com one of the figures from the film being shown at San Diego Comic Con appears to show Jared Leto's Joker in a funned up Batman costume. As it's part of a display showing all the main characters as they appear in the film it seems to suggest that this is something that appears in the movie itself.
There's also this version below, adding weight to the idea that this is something that happens in the movie and not just a weird variation.
If it is in the film it's going to be interesting to see how that works. Weird dream sequence? Or just the Joker showing just how craaaaaazy he can get.
Directed by David Ayer and starring Will Smith, Margot Robbie, Jared Leto, Viola Davis, Jai Courtney, and Joel Kinnaman, Suicide Squad will open in the UK and US on August 5, 2016.