Here's how stopping Boulder in Return of Boulder.
Narrator: At the yards, the other engines were collecting trucks, then they heard Boulder!
Percy: (whistles) Oh, no!
Percy: It's that boulder from before! And it's heading straight for us!
[Boulder is rolling right towards them!]
Astrid: That rock is heading straight for the yards!
Hiccup: What do we do?!
Fishlegs: You see that pile of rocks over there?S
Fishlegs: If we can blast them down, it should divert the boulder away from the yards and then into that pond over there! [points to it]
[Soon they then start having the dragons fire fire bombs at the rock pile's bottom as the pile slightly shakes]
Hiccup: Okay bud, give it your best shot!
Toothless: [fires a powerful Plasma blast]
[when the blast hits the rock pilew it then falls over and makes a stop block, as Boulder rolls in. Then Boulder is diverted by the rock block and then rolls into the pond with a loud splash!]
[Soon they fly over Boulder]
Apple Bloom: Looks like we got ourselves, a hook, line, and sinker!
Scootaloo; Nice one, Fishlegs! We finally stopped that rock!
Fishlegs: No problemo.
Button Mash: I'll give Sir Topham Hatt a call right now!
[later on, Sir Topham Hatt expected the damage]
Narrator: As Rocky lifted Boulder out of the pond, Sir Topham Hatt looked crossly at it.
Sir Topham Hatt: Once again, this boulder has caused a lot of damage to the railway!
Apple Bloom: What now sir?
Sir Topham Hatt: Well, I've given it some real good thought, and I think the best thing to do for this boulder is to return it to the same cliff where was from the start.
[it fades to Boulder right on his original spot]
Narrator: There on Boulder's mountain, was Boulder. As down below, Rusty gazing up from a safe distance as Boulder is smiling.
Rusty: Well it may of taken a few years, but at long last, Boulder is now at peace.
[Then Boulder turns to Rusty]
Boulder: Thank you, Rusty. My friend. [his face disappears]
Rusty: Huh? [does a double take as he looks at Boulder] Huh, I could've sworn I just heard Boulder thank me. Maybe he really is alive. Oh well. [he then leaves]
Narrator: And Rusty hoots his horn goodbye, as he went back to the sheds.
Boulder: [his face appears again and he winks at the audience]
[the episode ends with "Pokémon: Galactic Battles ending"]