Alien Alert is a feature-length special. It was released in UK cinema's on the 17th of June 2017 and was released on DVD in the UK on October 2nd.
Pontypandy is hit by a raft of UFO sightings and Fireman Sam is determined to get to the bottom of this mystery.
- Fireman Sam
- Penny Morris
- Elvis Cridlington
- Arnold McKinley
- Ellie Phillips
- Station Officer Steele
- Tom Thomas
- Ben Hooper
- Sarah and James
- Bronwyn Jones
- Charlie Jones
- Gareth Griffiths
- Hannah Sparkes
- Lizzie Sparkes
- Joe Sparkes
- Mandy Flood
- Helen Flood
- Mike Flood
- Norman Price
- Dilys Price
- Lily Chen
- Mrs. Chen
- Trevor Evans
- Moose Roberts
- Bella Lasagne
- Wallaby 2
- Mountain Rescue Ambulance
- Nurse Flood's Car
- Trevor's Bus
- Mike's Van
- Veterinary 4x4
- Charlie's Fishing Boat
- The Pontypandy Flyer
- The Skiff
- Dilys' Car
- Buck's Jet Ski
- Steven Kynman as Sam, Elvis, Norman, and Charlie
- Tegwen Tucker as Penny, Sarah, Bronwyn, and Mrs. Chen
- David Carling as Station Officer Steele, Trevor, Tom and Mike
- John Hasler as James and Arnold
- Su Douglas as Dilys, Mandy, Helen and Lily
- Alex Lowe as Ben and Joe
- Ifan Huw Dafydd as Gareth
- Nigel Whitmey as Moose
- Jo Wyatt as Hannah and Lizzie
- Harriet Kershaw as Ellie and Bella
- David Tennant as Buck Douglas
- This is the last Fireman Sam project to be animated by Xing Xing.
- This special introduces Buck Douglas and his cameraman.
- This special also introduces Wallaby 2, Nurse Flood's 4x4 Ambulance & the Search & Rescue team
- First time Dilys is seen driving a vehicle.
- This is the first time since Snow Business that Bella is featured in a special.
- It was broadcast on Channel 5 on the 28th of October 2017 & on Cartoonito on the 11th of November 2017.
- Buck Douglas’ name is partially a reference to the titular character of Buck Rogers.
- His character model is based on the Tenth Doctor (as played by his voice actor, David Tennant, in the popular BBC Sci-Fi Series ‘’Doctor Who"
- James’ line, ‘In the woods, no one can hear you scream’, is a reference to the quote ‘in space, no one can hear you scream’, a tagline used to advertise Ridley Scott’s 1979 cult Sci-Fi/Horror movie, Alien.
- Sarah refers to her Uncle Sam as "Fireman Sam" at one point, but corrects herself later on.