GameGuide

This episode should take no more than twenty minutes. It’s fast and fairly easy.
Homer finds Bart in an alley. He will ask Bart if he wants to go into the sewer with him and shoot rats with a shotgun. Bart then turns into Bartman.
Use Bart to double-jump across the ravine. Once across, destroy the boxes and bats with his sling shot. You can now enter the temple.
You must now cross the chasm. Step on the left pressure pad to trigger the ledges. Have Bart climb the ledges that project out and then have Homer step on the right pressure pad to trigger the other ledges. Once they are out, have Bart climb to the top.
Tip: If Homer steps off of the right pressure pad while Bart is on the ledge, the ledge will recede and Bart will fall.
Once Bart is at the top of the statue, turn him into Bartman and jump to the platform in the center of the chasm. A bridge will come out for Homer to cross.
Have Bart climb the wall on the right hand side and push the bounce pad down for Homer to jump on. Once Homer is up on the ledge step on both pressure pads to activate the opening of the wall.
Get both Homer and Bart onto the Dinosaur fossil in the middle of the next room by climbing the adjacent ladder. Security guards will emerge, but you can take down the first wave if you position both Homer and Bart on top of the fossil. Have Homer walk to the back end of the Dinosaur. Then have Bart turn into Bartman and go to the front, do a double jump and float to the ledge. Take it to the other side. Once across, open the door for Homer.
In the next room there are more security guards. Have Homer activate the switch by the volcano. This will provide an air stream for Bart. Use the cape to get to the pterodactyls. Walk to the white spot on the wing and he will be bounced to a wire hanging over the room.
Ride the wire and drop down on top of the tree, then jump up the branches to the top. At the top Bart needs to use his slingshot near the white light on the tree. There is a target directly in front of him. When the target is hit, the doors open to the next area.
Some guards will come out of the next room. Destroy them and then have Bart step on the right pressure pad. This will turn Bart into RoboBart. Now he can fire lasers through glass temporarily, which will be enough to get through the next few rooms. If he runs out, he can go back and get the lasers again.
Go through the next corridor which is a panorama display in the museum. Use the RoboBart function to shoot the targets in order from start to finish to force Jimbo’s thug out of the display. Along the way there are platforms where Bart can recharge RoboBart.
Tip: Once Jimbo’s thug runs out, turn into Homer and fight them.
Proceed into the next room, which is the space exhibit.
Have Bart climb the wall in Bartman-mode and do a double-jump. Glide to a jet of hot air, which will take him to a jet that is not producing air. While Bart is on the jet, switch to Homer and activate the jet, allowing Bart to glide to the remaining jets.here.

The Simpsons Bartman Begins Video Walkthrough