|Why do the costumes in the display case look like the ones in Batman Gotham Knights and not the ones used in Justice League Unlimited? |
First off, the characters Robin, Nightwing, and Batgirl never appeared in Justice League Unlimited so we are left to assume that they never changed their costumes. The main difference is that Batman changed his costume. This show was made before Justice League Unlimited.
An interesting fact would be that Bruce Timm was going to keep the same designs, though James Tucker convinced him to change the design. So, if you want to blame anyone for the change -- blame James!