Lenny Loosejocks in Space/Venus

Mercury is a planet with mushrooms large as trees. It has a huge volcano with the bomb is housed inside of it.

Your first goal is the lever at the very furthest to the right. Simply flip it, it opens the door inside the volcano. Don't flip the lever at the back of the volcano.

The second goal is creating a bridge over the lava. To do so, stand still in the open area between two mushrooms. A pterodactyl will give you a ride to the top of the volcano. Once up there simply drop the rocks into the volcano to make the bridge. Afterwards simply climb down the ladder.

Finally just walk into the cavern of the volcano. If you took care of the lever and bridge the path to the bomb should be clear. If the guard dog next to the bomb is in the way then you've flipped the lever on the back of the mountain, go back and unflip it.

Bomb disarming
It's a sliding block puzzle.

Once the bomb is disarmed, note the digit that appears and walk back to the space ship to complete this planet.