The Mountain

The Mountain is the main obstacle in The Little Engine That Could. Its appearance and role vary depending on the movie or book.

Original Appearance And Role
In the original book by Watty Piper, the Mountain appeared more like a stereotypical hill than a mountain. It only had a single track that ran down the middle. This version of the Mountain appears much easier to climb than the other depictions, surely easy for the Little Engine. Some versions of the book depict a storm building as the Little Engine climbs, but she ultimately rounds the summit and descends down the track to the town.

The 1991 Movie
In the 1991 Movie, the Mountain is shown in the opening titles as more mountain-like. It has a pointed peak and even has clouds near the summit. A major change to the Mountain's appearance it also revealed in the opening credits, being the rather precarious path that winds over the mountain, which includes crudely constructed bridges and a scary looking cave.

Perhaps the most puzzling thing about the Mountain is that only Tillie seems to have a hard time going over the Mountain, while the other engines are able to speed along without giving much thought to it. My guess is that Tillie, having never left the yard until this point, took the path shown in the opening credits under the assumption that she was going the right way. Georgia turned on to said track shortly before she broke down, indicating that the other engines use a track that isn't nearly as hazardous as the track Tillie took. It would've made sense to considering the seemingly crude appearance of the track and bridges, making them unable to support heavy engines, like Farnsworth and Pete. Even Georgia would've crushed any of those bridges. Thus, it's safe to say that Tillie, assuming she was on the right track, went over the Mountain using tracks only she was small and light enough to use, unaware of the safer track the other engines used.

The 2011 Movie
Again, the Mountain's appearance is mountain-like, but its role is changed completely. Instead of being a mere obstacle, it serves as a vital barrier between the Real World and Dreamland. It also has a tunnel going through it that collapses and causes a crisis. The track that goes over it is unused due to how dangerous it was to take it, which is what led to the Tunnel's construction.

When Little Engine takes the Mountain Track, she comes across and engine who inhabits the same tracks with different intentions, the Nightmare Train. He is derailed toward the end of the film, but the encounter nearly causes Little Engine to give up entirely.

Tom and Jerry version of the 1991 movie
The Mountain's appearance is mountain-like just like the original 1991 film, with its role is now expanded in Tom and Jerry & The Little Engine That Could. It is remained as the main obstacle and located in Little Golden Book Land between Harbortown and the Big City. The old tracks that leads to crudely constructed bridges and a scary-looking cave shown in the opening credits is unused due to how dangerous it was to take it, which is what led to the construction of the new safer track, which includes a tunnels and rust-proof iron bridges.

Like the original film, Tillie struggles to get up the mountain, but Farnsworth and Pete make it up the mountain and back just fine and they're heavier than her. Casey Junior climbs up the mountain summit references to Dumbo. Tuffy called the Mountain a "big tall mountain". When Tillie takes the old Mountain Track, she comes across and engine who inhabits the same tracks with different intentions, the Ghost Train. Its summit is where the chase between Tillie, Tom, Jerry, the Alley Cats and the Ghost Train. It is derailed toward the end of the film, but the encounter almost makes Tillie give up entirely.

Games
The Mountain appeared in every Sailor Moon game.