LEGO Batman

After you get Super Hero In all the Hero levels, go to the trophy room and in the corner will be a staircase to the Wayne Manor bonus level.

There aren't a lot of actual studs to collect, though they are all of high value (ie: 10,000). There are basically three areas/tasks to collect studs.

1. The super mario level. On the far left side of the Wayne Manor patio are some barrels, destroy them with batarang and build a computer from the pieces. Electronic whiz Robin can then activate the computer by using the control panel. You may have to use it a few times. Then sit in the seat and spin, eventually you'll go to the super mario level. In this level the studs are in blocks in the ground, above you and pretty much everywhere you don't look. Use batarang and bombs to find them.
The Total value of studs in this level is 470,000.
(according to a comment there may actually be 480,000 value to the studs in this level, you need to get at least 470,000, you get more, great :)

2. The annoying bomb and ramp and spinner level.
Kick the soccer like explosives around and blow up the spinners. Or drag them with the hover vehicles.
The total value of studs in this level is 500,000

3. Mowing the lawn and two other studs.
When you finish the mario level you end up on the roof by another computer. There is a stud up here.(10,000)
When you finish the annoying explosive spinner level you end up on a different roof, there is a stud up here. (10,000)
IF you build the bulldozer on the far right side of the Wayne Manor patio you can then bulldoze the grey rocks in the lawn.
When they are bulldozed, a door will open revealing the lawn mower. Now mow the flowers that sprouted where the rocks had lain. When they are mowed a stud (10,000) will appear in the lawnmower shed.
Total number of studs outside 30,000

Thus 1mil.
*BONUS: According to the comments this achievement is also unlockable for the co-op player, I have not tested this, but if so, Awesome :) !

Complete every mission on the Hero's side with a Super Hero rating to unlock this bonus level. Here are some codes that will help you get a Super Hero rating on any level:
Score x2 Multiplier N4NR3E
Score x4 Multiplier CX9MAT
Score x6 Multiplier MLVNF2
Score x8 Multiplier WCCDB9
Score x10 Multiplier 18HW07

Here's a video walkthrough on how to complete the bonus level itself. Took me about an hour to do. Credit for the video goes to YouTube user "UltraBartman".
Edit Reported Content Team: The video has been removed as it no longer exists.

This is for getting super hero on every hero level, and can be found in the trophy room in the left corner.

There was one block I completely missed in the Mario world. So I looked up a video guide and found it. Below is the video, hope this helps.

Credit for video goes to packattack04082

First you have to complete the Hero story mode with a Super Hero rating on every level, then you will be able to access this level in the trophy room. To complete it, you must collect one million studs. There are exactly 1,000,000 total so you must find every single stud. Use the walkthrough found here:
http://www.xbox360achievements.org/forum/showpost.php?p=1202...
to do it successfully.