Mountain Marvel is the fourth episode of the twelfth season.
Peter Sam rushes to finish his jobs in order to hear a tale about Proteus from the famous storyteller, Miss Marvel. During this, he stumbles across a neglected statue of Proteus and vows to hide it until the ceremony. This results in a disaster, but Peter Sam figures out a way to fix everything and make it in time for the storytelling - complete with the statue on display.
- Peter Sam
- Mighty Mac
- Mr. Percival
- The Engineer
- Miss Marvel (does not speak)
- Skarloey (cameo)
- Rheneas (cameo)
- Sir Handel (cameo)
- Rusty (cameo)
- Farmer Trotter (cameo)
- Thomas (mentioned)
- Proteus (mentioned; seen as a statue)
- In France, this episode is called "The Legend of Proteus". In Germany, this episode is titled "Peter Sam's Discovery".
- Sir Handel is not with the other engines at the storytelling.
- This episode marks Mighty Mac's last speaking role to date.
- When Peter Sam discovers the statue of Proteus, his milk churns disappear.
- When Mighty Mac first meets Peter Sam, a steam platform is visible on the track next to him.
- When Peter Sam crashes into the buffers, you can see something on the ground which was used to make the trucks lift up into the air.
- When Peter Sam crashes into the buffers the junction's layout changes from what it was earlier in the episode.
- When Mighty Mac leaves to tell Mr. Percival about the statue, there is no steam coming from Mac's funnel. Also, Freddie is derailed.
- Proteus' magic lamp is missing from the statue, and it also has different pistons from Proteus' appearance in The Magic Lamp.
- Peter Sam has Freddie's whistle sound.
- In the last shot of Rusty, part of a face marker is visible under his chin. These markings were used to indicate where the engines' faces should be during production of the twelfth season.
- When Peter Sam pulls the statue away, the flatbed is derailed.
- Brakevans should have been added to Sir Handel, Skarloey, Peter Sam, Mighty Mac, Freddie, and Duncan's trains.
- Mr. Percival now has a full head of hair under his hat, even though he was depicted with a bald head in A Smooth Ride.