is a human character.
The Search for the Controllers
In Sierra's first appearance, she, along with
, Jacob , and Cassie , came to Sodor for the first time to visit Caroline and her family Kira . Sometime between the special and  , Jacob and Sierra decided to stay on Sodor.
Rosie, Jacob, Sierra, an d t he Troublesome Trucks
Later on, Sierra, Jacob, and
were taking a train of stone from Rosie Anopha Quarry to Brendam. However, Jacob was very impatient, and did not wait for a brake van before leaving the quarry. Because of this, they had trouble getting up Gordon's Hill until , Cassie, and Kira came along and helped them up the hill. However, Jacob did not want to stop to uncouple Oliver, and this lead to Rosie and Oliver having an accident in Oliver Henry's Forest . Sierra and Jacob later convinced  Sir Topham Hatt to restore Glynn and threw surprise birthday parties for Cassie  and Caroline  .
Later, Jacob and Sierra were left in charge of the
North Western Railway while Richard Hatt's family went on holiday, much to the dismay of and Marie Rose .
Sierra is a very loving and caring girl. She is also determined and very persistent.
Sierra can almost always be found wearing either yellow or purple.
What's wrong guys?" " Oh, nothing. We're just a little homesick." " But, Miss Sierra, how could you be sick of a wonderful place like Sodor?" " No, Toad homesick means that we miss our home, not that we're sick of yours." " Oh, sorry, Mr. Jacob." " That's alright, Toad. After, all you gave us a good laugh. — , Duck , Sierra , and Jacob , Toad , Homesick
I don't think it's very wise of Mr. Hatt to leave those two immature children in charge of us." " They're not children anymore, Marie. They're 16 now." " And anyway, they've been on Sodor, taking care of themselves for like 3 years now. I think if they can take care of themselves for that long, then they can certainly take care of all of us for a week." " They're still young, and they surely aren't responsible enough to take care of a railway as big as this one." " I hate to admit it but, Marie’s right. This railway should not be left in the hand of two incompetent and irresponsible children. — , Marie , Rosie , and Madison about Rose and Jacob , Sierra , The Substitut e Controller
Sierra is one of only two characters to be the main character in at least one episode in every season, with the other being Jacob.
Jacobacranmer, Sierra's creator, based her on his best friend.
Episodes Emily to the Rescue | Memories | Saving Benjamin | Rosie, Jacob, Sierra, and the Troublesome Trucks | Back In Service | Dockyard Tales | Homesick | Childhood Memories | The Best Start to Summer | Jacob and Rylie's Blue Mountain Adventure | Cassie's Birthday Surprise | A Surprise for Jacob | A Birthday Surprise for Caroline | Sir Handel and the Baking Soda | Toby and the Subway Car | Earls and Passengers | Trouble for Diesel 10 | Jacob and the Famous Visitor | Smudger Returns | Donald, Douglas, and the Trouble With Leaves | Gordon and the Railway Choice Awards | No Hamburgers for Duck | Emily's Arianating Experience | Paxton and the New Diesel | Murdoch's Money Madness | Harvey and the Railway Inspectors | Butch Proves a Point | Home, Sweet Home ( | ) cancelled Jacob's Unlucky Day ( | ) cancelled Gordon and the Famous Singer ( | ) cancelled The New Bridge (
Transcripts Emily to the Rescue/Transcript | Memories/Transcript | Saving Benjamin/Transcript | Rosie, Jacob, Sierra, and the Troublesome Trucks/Transcript | Back In Service/Transcript | Dockyard Tales/Transcript | Homesick/Transcript | Childhood Memories/Transcript | The Best Start to Summer/Transcript | Jacob and Rylie's Blue Mountain Adventure/Transcript | Cassie's Birthday Surprise/Transcript | A Surprise for Jacob/Transcript | A Birthday Surprise for Caroline/Transcript | Sir Handel and the Baking Soda/Transcript | Toby and the Subway Car/Transcript | Earls and Passengers/Transcript | Trouble for Diesel 10/Transcript | Jacob and the Famous Visitor/Transcript | Smudger Returns/Transcript | Donald, Douglas, and the Trouble With Leaves/Transcript | Gordon and the Railway Choice Awards/Transcript | No Hamburgers for Duck/Transcript | Emily's Arianating Experience/Transcript | Paxton and the New Diesel/Transcript | Murdoch's Money Madness/Transcript | Harvey and the Railway Inspectors/Transcript | Butch Proves a Point/Transcript
Episode Galleries Emily to the Rescue/Gallery | Memories/Gallery | Saving Benjamin/Gallery | Rosie, Jacob, Sierra, and the Troublesome Trucks/Gallery | Back In Service/Gallery | Dockyard Tales/Gallery | Homesick/Gallery | Childhood Memories/Gallery | The Best Start to Summer/Gallery | Jacob and Rylie's Blue Mountain Adventure/Gallery | Cassie's Birthday Surprise/Gallery | A Surprise for Jacob/Gallery | A Birthday Surprise for Caroline/Gallery | Sir Handel and the Baking Soda/Gallery | Toby and the Subway Car/Gallery | Earls and Passengers/Gallery | Trouble for Diesel 10/Gallery | Jacob and the Famous Visitor/Gallery | Smudger Returns/Gallery | Donald, Douglas, and the Trouble With Leaves/Gallery | Gordon and the Railway Choice Awards/Gallery | No Hamburgers for Duck/Gallery | Emily's Arianating Experience/Gallery | Paxton and the New Diesel/Gallery | Murdoch's Money Madness/Gallery | Harvey and the Railway Inspectors/Gallery | Butch Proves a Point/Gallery
Characters With Main Roles
| Emily | Brady | Olivia | Kylie | Benjamin | Rosie | Jacob | Sierra | Thomas Glynn | Rylie | Cassie | Caroline | | Skarloey | Rheneas Sir Handel | | Toby | Percy Diesel 10 | Smudger | Duke | | Gordon | Duck | Donald | Douglas Paxton | | Murdoch | Harvey | Butch Fergus (
| Brady | Olivia | Kylie | Benjamin The Other Railway Diesels | | Jacob | Kira | Sierra Cassie | Rylie | Maddox | Brady the Human | Caroline
Episodes Sierra's Birthday Adventure | James and the New Engine | A New Friend for Rosie | Maddox and the Signal | Diesel's New Friend | Insignificant | Blisters | Twin Day | James' Day Out | Murdoch and Neville | A Dirty Day for Daniel | An Arlesdale Adventure | A Bad Day for Diesel | A Day for the Diesels | Quadruplets | Quads, Quarries, and Quarrels | Kids and Quarrels | Paige Returns | Crystal Island Adventure | Little Engines Can Do Big Things | Jack of Many Trades | Marion Makes a Move | Rosie's Old Friend | Rose's Backstory | Marie's Backstory | Dawn and Levi's Backstory | Jacob, Sierra, and Rylie's Backstory | Football | Brady and the Famous Visitor
Transcripts Sierra's Birthday Adventure/Transcript | James and the New Engine/Transcript | A New Friend for Rosie/Transcript | Maddox and the Signal/Transcript | Diesel's New Friend/Transcript | Insignificant/Transcript | Blisters/Transcript | Twin Day/Transcript | James' Day Out/Transcript | Murdoch and Neville/Transcript | A Dirty Day for Daniel/Transcript | An Arlesdale Adventure/Transcript | A Bad Day for Diesel/Transcript | A Day for the Diesels/Transcript | Quadruplets/Transcript | Quads, Quarries, and Quarrels/Transcript | Kids and Quarrels/Transcript | Paige Returns/Transcript | Crystal Island Adventure/Transcript | Little Engines Can Do Big Things/Transcript | Jack of Many Trades/Transcript | Marion Makes a Move/Transcript | Rosie's Old Friend/Transcript | Rose's Backstory/Transcript | Marie's Backstory/Transcript | Dawn and Levi's Backstory/Transcript | Jacob, Sierra, and Rylie's Backstory/Transcript | Football/Transcript | Brady and the Famous Visitor/Transcript
Episode Galleries Sierra's Birthday Adventure/Gallery | James and the New Engine/Gallery | A New Friend for Rosie/Gallery | Maddox and the Signal/Gallery | Diesel's New Friend/Gallery | Insignificant/Gallery | Blisters/Gallery | Twin Day/Gallery | James' Day Out/Gallery | Murdoch and Neville/Gallery | A Dirty Day for Daniel/Gallery | An Arlesdale Adventure/Gallery | A Bad Day for Diesel/Gallery | A Day for the Diesels/Gallery | Quadruplets/Gallery | Quads, Quarries, and Quarrels/Gallery | Kids and Quarrels/Gallery | Paige Returns/Gallery | Crystal Island Adventure/Gallery | Little Engines Can Do Big Things/Gallery | Jack of Many Trades/Gallery | Marion Makes a Move/Gallery | Rosie's Old Friend/Gallery | Rose's Backstory/Gallery | Marie's Backstory/Gallery | Dawn and Levi's Backstory/Gallery | Jacob, Sierra, and Rylie's Backstory/Gallery | Football/Gallery | Brady and the Famous Visitor/Gallery
Characters With Main Roles
| Sierra | James Ralph | | Rosie | Madison Maddox | Diesel | Rose | Dawn | Levi | | Marie | Spencer Blister I and Blister II | | Bill and Ben | Murdoch | Neville Daniel | Hank | Dailey | Dawson | Damian | David | | Jacob Paige | Mallory | Rex | Jack | Marion | James (human) |
Ralph | | Madison Rose | Dawn | Levi | | Marie | Spencer Blister I and Blister II | Daniel | Dailey | Dawson | Damian | David | Paige
Episodes Jacob, Meg, Sierra, and the Snow | Jacob's First Skate | Marion and the Miniature Engines | The New School | Marion and Ned | Marion and Daisy | Keeping to the Timetable | Jacob, Sierra, and Bradford | Geoffrey's Real?! | Stuck In The Snow | Sidney's Commitment | Gordon's Express Delivery | The Blind Engine | Solutions | Best Friends Day | Blown Away | Jacob, Sierra, and Hugo | Jacob, Sierra, and Lexi | Jacob, Sierra, and Theo | Journey Beyond Knapford | Jacob, Sierra, and Merlin | Hugo and the Dinosaurs | Jacob and Sierra's Birthday Shock | Amethyst's First Snow | The Old Repair Yard | Importance | Untitled Cancelled Episode (
Characters With Main Roles
Hank | Jem Cole | Jacob | Sierra | Amethyst | Hugo | Merlin | Madison | Rosie | Hurricane | Frankie | Lexi | Theo | Skiff | Thomas | Percy | Mia | Frank | Gordon | Sidney | Duck | Geoffrey | Bradford | Samson | Marion | Daisy | Ned | Meg | Mike | Rex | Bert | Raphael (
Episodes Meg and Molly | The Amusement Park | Extraordinary Engines | Hugo and the New Engine | Dylan's Backstory | Bill, Ben, and BoCo | Duck's Special Special | The Substitute Controller | All About George: A New Beginning | James' Jealousy | Another Day Gone | Greens vs Yellows | Mavis Figures It Out | Rosie's Secret | Iron Horse | Vandals | The Return of Vinnie | Oliver and the Mainland Exploration | Jacob, Sierra, and Kira's Experience in Driving | Demo Day | Murdoch and Arthur | Daisy and Harvey | It's Possible... | Philip the Lucky Engine | Good Effort | Arthur Takes the Kipper
Transcripts Meg and Molly/Transcript | The Amusement Park/Transcript | Extraordinary Engines/Transcript | Hugo and the New Engine/Transcript | Dylan's Backstory/Transcript | Bill, Ben, and BoCo/Transcript | Duck's Special Special/Transcript | The Substitute Controller/Transcript | All About George: A New Beginning/Transcript | James' Jealousy/Transcript | Another Day Gone/Transcript | Greens vs Yellows/Transcript | Mavis Figures It Out/Transcript | Rosie's Secret/Transcript | Iron Horse/Transcript | Vandals/Transcript | The Return of Vinnie/Transcript | Oliver and the Mainland Exploration/Transcript | Jacob, Sierra, and Kira's Experience in Driving/Transcript | Demo Day/Transcript | Murdoch and Arthur/Transcript | Daisy and Harvey/Transcript | It's Possible.../Transcript | Philip the Lucky Engine/Transcript | Good Effort/Transcript | Arthur Takes the Kipper/Transcript
Galleries Meg and Molly/Gallery | The Amusement Park/Gallery | Extraordinary Engines/Gallery | Hugo and the New Engine/Gallery | Dylan's Backstory/Gallery | Bill, Ben, and BoCo/Gallery | Duck's Special Special/Gallery | The Substitute Controller/Gallery | All About George: A New Beginning/Gallery | James' Jealousy/Gallery | Another Day Gone/Gallery | Greens vs Yellows/Gallery | Mavis Figures It Out/Gallery | Rosie's Secret/Gallery | Iron Horse/Gallery | Vandals/Gallery | The Return of Vinnie/Gallery | Oliver and the Mainland Exploration/Gallery | Jacob, Sierra, and Kira's Experience in Driving/Gallery | Demo Day/Gallery | Murdoch and Arthur/Gallery | Daisy and Harvey/Gallery | It's Possible.../Gallery | Philip the Lucky Engine/Gallery | Good Effort/Gallery | Arthur Takes the Kipper/Gallery
Characters With Main Roles
Meg | Molly | Dylan | Hugo | Bill and Ben | BoCo | Duck | Jacob | Sierra | George | James | Greg | Harvey | Bulstrode | Marie | Brady | Mavis | Rosie | Toby | Thomas | Annie and Clarabel | Vinnie | Oliver | Kira | Murdoch | Arthur | Daisy | Beresford | Philip | Richard Hatt