The Joker unlocked - unlocked from level 1
Batman unlocked - unlocked after completing level 12
This can be done during your story progression on level 12, or at any other time after this in the hub area or while replaying a level.Achievement
Once in hub hold the
button to bring up the character selection screen now:
Scroll across 14 tokens on the first row for Batman
Change to your second playable character by tapping
Once again hold
for character selection, scroll down to the 4th row and 10th token across and select the Joker.
Now being in control of the Joker stand near Batman then, tap
to go into Selfie mode move the left analogue so both are in image and press
to take photo.
Sorry, this Game Clip has been removed
As soon as pressed pop achievement unlocked.