Ok for this Secret achievement you have to do the following:
Set both Free Play Characters as The Joker and The Joker Animated SerirsDo do this you first need to play and complete the dlc story mission, then you will unlock 8 Characters including The Joker Animated.
These are as follows:
Batman (B:TAS)
Phantasm
The Joker (B:TAS)
Harley Quinn (B:TAS)
The Mad Hatter
Bat-Man
Two-Face (B:TAS)
Captain ClownNow this is done if you load up the game or quit to Gotham City Free Play Roam and do the following:
The Joker Animated (B:TAS)Press and hold
to bring up your Character select screen, scroll to row 9 and go across to character tile 20 and select with
.
Then tap
to change to your second free roam character
The JokerNow press and hold
once again to open up character select screen, scroll to row 4 and go across to character tile 10 and select with
.
As soon as you have done both pop achievement unlocked!
Congratulations!
Happy Hunting