i take no credit for the guide here is where it comes from http://www.cheatcc.com/pc/sg/lego_batman_2_dc_super_her....txt
Super Hero at 90,000
Characters: Batman, Robin
The Chase -
There's only one area to this, and it's entirely in vehicles. Your
objective is to shoot up the Joker Robot while it chases you through the
streets. First, keep an eye on the sides of the streets for silver. There
are silver supports holding up statues. Blast them and the statues will
topple onto the robot. Now, you're able to hammer on the robot's chest.
You'll need to do this a total of three times.
That's it! That's all you have to do in this mission! It's pretty quick.