I have always been fascinated by toys featuring removable masks and disguises.  I wanted a "In the Batcave" version of the dynamic duo.

I took standard Batman (had to repaint one of the colored variants as I didn't have an extra "Combat Belt" version at  the time.) and Robin figures and removed their heads via the standard "boil and pop" method.  I then installed the heads of  Bruce Wayne and Dick Grayson.