The train that goes down to the Hall of Heroes is occupied by Blarg Soldiers!Mission description
Ride the train to the Hall of Heroes is a mission in Ratchet & Clank taking place in Aleero City on planet Kerwan. After Al advised Ratchet and Clank to use the grav-train near his roboshack to return to the Hall of Heroes and train with Brax Lectrus, they found the A train to the Hall of Heroes occupied by the blarg, with a bomb on the train that would be sent to the Hall of Heroes to destroy it. The two had to ride the grav-train and disconnect the front from the rest of the train, stopping the bomb.
After entering the train station by climbing the stairs in the entrance, first head to the right, climbing a few stacked crates with the Helipack boost jumps and jumps, then stretch jump across to the top of a large stack of crates. Behind this is a gold bolt and a group of breakable crates with bolts. Obtain them, then climb back over with the Helipack to leave.
Head towards the train cart (left from the entrance) and defeat the blarg commander and robomutts here (easily dispatched with a Proton Drum and/or Fusion Grenade), then use the Swingshot to pull towards the versa-target for the first train and then towards the second, defeating the blarg commanders here with a Combuster first. This will land you on the grav-train to the Hall of Heroes, and the train will begin to depart.
Along the train, first head forwards in a linear direction. One of the carts in front contains a group of construction pipes with green buttons to release them, fire at the buttons and the blarg commander perched on top will fall to his death. Use the bolt crank on the next train to extend the versa-target in front to the right, then use the Swingshot to swing across it to the next cart. The crates here actually contain robomutts, so destroy them with a Fusion Grenade or Proton Drum instead, then continue moving. The next cart is inaccessible due to an orange forcefield around two stashed ships, but throw your OmniWrench at the green button and they will fall off, allowing you to proceed.
The next cart holds a container with deadly fish. Jump to the ledge and shimmy across with the stick, then jump up the ledges to the top of the cart. The next cart contains two tentacles that will attack Ratchet, which are stopped by throwing an OmniWrench. Defeat the blarg commanders in front with the Combuster before heading to the cart in front and shimmying across the ledges to reach the top of it, then destroy the blarg heli-commander (best defeated with the Combuster, making sure to hide behind the box in front to avoid its lasers) causing it to free space in the cart in front. Proceed forward, defeating the blarg commander and blarg heli-commanders here, before traversing the next cart containing a bomb and then traveling to the next cart to turn the bolt crank. This will disconnect the front of the train from the cart with the bomb, and the mission will be complete as you then travel to the Hall of Heroes. Here, you commence the planet's final mission, "Complete fitness course".