Emily is a large Stirling Single tender engine.
When Emily was new to Sodor, she was ignored by the other engines for pulling Annie and Clarabel without Thomas' permission or knowledge. The matter was resolved after she saved both Thomas and Oliver from a nasty accident on the cross-points, and she was rewarded with two new coaches. Emily proved to be kind-hearted, as she was the only engine concerned about Henry when he was ill due to leaky tubes and when she stuck up for Salty when Thomas and Percy were teasing him.
However, Emily has proven to be a nuisance on occasion as she bossed everyone about when they were clearing up after a storm; Thomas when taking passengers, and Percy when shunting trucks. When pulling the express for the first time, she was determined to keep to Gordon's timing, only to run out of water.
When Thomas had to stay at Knapford Sheds, Emily did not like his company at first as she just wanted some sleep. However, she learned how comfortable it is to have the company of friends and once Tidmouth Sheds was rebuilt, she was transferred there to be with her new shedmates.
Like most engines, Emily can get quite puffed up in the smokebox. When she was called "Excellent Emily", she ignored the advice of Murdoch, Thomas, and Duck only to get herself into trouble. Afterwards, she took their advice to get her job done.
Emily tries her best to make her friends happy. When she assumed that Mavis was sad, she took flowers to the quarry, but only created a mess. When she tried to help her friends with the football match, she neglected to fetch the dirty washing, which turned out to be the football team's uniforms. Also, when the Fat Controller lost his top hat, Emily went to find it without success and then took the special Christmas train without permission. However, she always makes amends for her friends' sake.
She later took Paxton to the Sodor Dieselworks after he was damaged during an accident at the Blue Mountain Quarry.
When Thomas hid his snowplough, Emily had to do Thomas' work and saved him when he got stuck in the snow.
Thomas told Emily about the "Flatbeds of Fear," but Emily did not believe in it and said there was an explanation. She eventually believed in it, until Thomas told her that it was just one of Salty's tall tales.
When the Steam Team try to clear the tracks of snow for Connor to deliver the last train for Christmas, Emily is unable to clear them from the Sodor side, but is happy to see Hiro as he clears it from the other direction, then is disappointed when they mistake Harold for Father Christmas by believing his red port lamp to be Rudolph's nose.
She was later informed by Paxton about the rumour that Toby was to be scrapped, but Henrietta overheard and knew it wasn't true. Emily took her to find Toby, and once they found him safe, Emily gave him some of her coal.
When Henry confided in Emily that he feared catching Chicken Pox from Stephen and Bridget Hatt, she assured him that he could not get chicken pox, joking that he worries too much.
In the seventh season, Emily acts as a sisterly figure to the others. Emily is kind and friendly and always sensitive to the other engines' feelings. If she wrongs someone, knowingly or not, she is quick to apologize.
From the eighth season onwards, however, Emily can tend to get into trouble because of her fussy and bossy attitude, but she is nicer than she lets on. She seems to want to strive to be one of the best, and it sometimes causes mishaps, though she usually makes up for her mistakes when she realizes her errors.
From the seventeenth season onwards, however, her personality seems to be reverting as to how it was in the seventh season.
Emily is based on a GNR G Stirling Single; she has a taller funnel in place of her broken old one. The only surviving member of her class is on display at the National Railway Museum.
Emily is painted emerald green for the Great Northern Railway with gold and yellow lining. She has chocolate running-boards and her buffers were originally bronze but now are silver.
- Season 7 - Emily's New Coaches , What's the Matter with Henry?, Salty's Stormy Tale, Something Fishy (cameo), Peace and Quiet (cameo), Bulgy Rides Again, and Gordon and Spencer (cameo)
- Season 8 - James Gets a New Coat (does not speak), Thomas, Emily and the Snowplough, Don't Tell Thomas, Emily's New Route, Gordon Takes Charge (cameo), Spic and Span, Thomas and the Circus(cameo), Thomas Gets It Right (cameo), As Good as Gordon, Emily's Adventure, Halloween,Chickens to School, James Goes Too Far (cameo), and Percy and the Magic Carpet (cameo)
- Season 9 - Thomas and the Rainbow (cameo), Molly's Special Special, Thomas' Milkshake Muddle,Thomas and the Toy Shop (does not speak), Respect for Gordon, Thomas and the Birthday Picnic,Thomas and the New Engine, Toby Feels Left Out (does not speak), Thomas Tries His Best (cameo),Thomas and the Statue, Henry and the Flagpole (cameo), Emily Knows Best, Thomas' Day Off(cameo), Bold and Brave (cameo), Thomas and the Golden Eagle (does not speak), Keeping up with James (cameo), and Flour Power (cameo)
- Season 10 - Percy and the Funfair, The Green Controller (cameo), It's Good to be Gordon (cameo),Edward Strikes Out, Thomas and the Shooting Star (cameo), Big Strong Henry, Sticky Toffee Thomas (cameo), Thomas' Frosty Friend, Emily and the Special Coaches, Thomas and the Colours (cameo),Thomas and the Treasure, and James the Second Best (does not speak)
- Season 11 - Thomas and the Storyteller, Emily's Rubbish, Dream On, Dirty Work, Gordon and the Engineer (cameo), Thomas and the Spaceship (cameo), Henry's Lucky Day (cameo), Thomas and the Lighthouse, Thomas Sets Sail, Don't be Silly, Billy (cameo), Edward and the Mail, and Thomas in Trouble
- Season 12 - Thomas and the Billboard, Steady Eddie (does not speak), Rosie's Funfair Special,Henry Gets It Wrong, Heave Ho Thomas! (cameo), Toby's Special Surprise, Excellent Emily, Saved You! (cameo), Thomas Puts the Brakes On, and Percy and the Bandstand (cameo)
- Season 13 - The Lion of Sodor (cameo), Tickled Pink, Time For a Story (cameo), Percy's Parcel(cameo), Toby's New Whistle, A Blooming Mess, Thomas and the Runaway Kite, Steamy Sodor(cameo), Splish, Splash, Splosh!, The Biggest Present of All, Snow Tracks, Henry's Good Deeds(cameo), Buzzy Bees (cameo), and Hiro Helps Out (cameo)
- Season 14 - Thomas' Tall Friend (cameo), Pingy Pongy Pick Up, Toby and the Whistling Woods(cameo), Henry's Health and Safety (cameo), Pop Goes Thomas (does not speak), Victor Says Yes,Thomas in Charge (cameo), Merry Winter Wish (cameo), Thomas' Crazy Day (cameo), Thomas and Scruff (cameo), and Henry's Magic Box (does not speak)
- Season 15 - Emily and Dash, Percy's New Friends, Edward the Hero (cameo), Up, Up and Away!(cameo), Surprise, Surprise (cameo), Spencer the Grand (cameo), Kevin the Steamie, Percy the Snowman (cameo), Tree Trouble (cameo), and Fiery Flynn (cameo)
- Season 16 - Race to the Rescue (cameo), Ol' Wheezy Wobbles (cameo), Express Coming Through(cameo), Percy and the Monster of Brendam (cameo), Ho Ho Snowman, Flash Bang Wallop! (cameo),Thomas and the Rubbish Train, Bust My Buffers! (cameo), Thomas and the Sounds of Sodor, Salty's Surprise (cameo), Emily's Winter Party Special, Muddy Matters, Whiff's Wish, and Happy Birthday Sir!(cameo)
- Season 17 - Wayward Winston, Calm Down Caitlin (cameo), The Lost Puff (cameo), The Phantom Express (cameo), No Snow for Thomas, The Missing Christmas Decorations, The Frozen Turntable(does not speak), Gone Fishing (cameo), The Afternoon Tea Express (does not speak), The Smelly Kipper, and Thomas' Shortcut (cameo)
- Season 18 - Old Reliable Edward, Flatbeds of Fear, Signals Crossed (cameo), Duck in the Water(cameo), Duck and the Slip Coaches, Duncan and the Grumpy Passenger (cameo), Missing Gator(cameo), Spencer's VIP, Last Train for Christmas, Duncan the Humbug (cameo), The Perfect Gift(cameo), and Emily Saves the World
- Season 19 - Who's Geoffrey? (cameo), The Truth About Toby, Lost Property (cameo), Toad and the Whale (cameo), Henry Spots Trouble, Snow Place Like Home, Diesel's Ghostly Christmas, The Beast of Sodor, Very Important Sheep (cameo), Salty All at Sea (cameo), The Best Engines Ever!, and Helping Hiro (cameo)
- Calling All Engines!
- The Great Discovery
- Hero of the Rails
- Misty Island Rescue
- Day of the Diesels
- Blue Mountain Mystery
- King of the Railway
- Tale of the Brave
- Sodor's Legend of the Lost Treasure
- Teresa Gallagher (UK; Hero of the Rails onwards)
- Jules de Jongh (US; Hero of the Rails onwards)
- Blanche Ravalec (France and French speaking Canada; eighth season onwards)
- Yuka Shioyama (Japan; seventh and eighth seasons)
- Erina Yamazaki (Japan; Calling All Engines! onwards)
- Marit Berg (Norway; Hero of the Rails - seventeenth season)
- Marianne Westby (Norway; Day of the Diesels onwards, excluding the sixteenth and seventeenth season)
- Chiara Gioncardi (Italy)
- Diana Pérez (Latin America; Hero of the Rails onwards)
- Marjolein Algera (The Netherlands)
- Kristina von Weltzien (Germany)
- Joanna Pach-Żbikowska (Poland; Hero of the Rails onwards)
- Mia Kadosh (Israel)
- Kate Kelly (Brazil)
- María Sánchez (Spain)
- Susa Saukko (Finland)
- Ioana Perneș (Romania)
- Thanh Hống (Vietnam)
- Although the second female steam engine to ever appear (the first being Lady), Emily is the first female steam engine to appear and remain on a regular basis.
- One of Emily's models was on display in Canada at Nitrogen Studios, it is now part of the touring Thomas and Friends: Explore the Rails exhibit.
- Emily had the same whistle sound as Henry in the eighth season and from the thirteenth season until the latter half of the seventeenth. From the eighth to twelfth season, her whistle was a pitched-up version of Henry's. From the seventeenth season onwards, she receives a new whistle sound.
- In Railway Rhymes, the author states that Emily and Thomas act like brother and sister.
- According to a magazine bio, she has a particular fondness for James and treats him like a little brother.
- Emily is the only member of the Steam Team to not be created by Wilbert Awdry.
- Emily is incorrectly listed as being the number 6 engine on The Official Website.
- According to Robert Gauld-Galliers's concept art, Emily was originally going to have handrails on top of her smokebox and a gold symbol on her wheel arch.
- From the thirteenth to fifteenth seasons, Emily was incorrectly shown as emitting smoke from her safety valve.
- Emily has had many modifications throughout the television series. These include:
- Season 8:
- Her buffers changed from bronze to silver.
- Season 11:
- Her forward buffer housings' colour changed from black to red.
- Season 12:
- Her face became larger.
- Mid-Season 17:
- She received a permanent lamp, a taillamp, and lampirons.
- Season 19:
- She gains a brakepipe.
- Season 8:
- ERTL (discontinued)
- Wooden Railway (normal, talking, roll and whistle)
- Take Along (normal and metallic; discontinued)
- Motor Road and Rail (discontinued outside Asia)
- TrackMaster (normal and Splish, Splash, Splosh! versions)
- My First Thomas (normal and talking)
- Hornby (discontinued)
- Bachmann (HO and large scale)
- My Thomas Story Library (discontinued)
- Trading Cards
- Take-n-Play (normal and talking)
- Limited Edition Collection
- Mega Bloks (discontinued)
- Capsule Plarail (normal and metallic)
- Pocket Fantasy (discontinued)
- Woody Capsule Series
- Boss (with Milk Tanker; discontinued)
- Collectible Railway
- Padlock and Key
- Minis (classic, spooky, sweets and DC super friends)
- Rail Rollers