- "I take pride in my appearance. What's wrong with that?"
- ―Isobella, Serendipity
Isobella is a yellow vintage steam Lorry that works for Miss Jenny Packard.
Isobella is a valuable member of The Pack, working hard on construction and occasionally Sodor Shipping. She is close friends with Kelly, who had rescued her from falling off a bridge on a windy day.
Isobella was thrilled to see Butch after his long absence. She bid him farewell as he left for his next assignment, but she would see him again sooner than she would have expected! When Butch broke down, Isobella crashed into Butch's back bumper and gave him a nasty dent (plus a few unwanted scrapes on Isobella's fender and paintwork). Flustered, she left the very downtrodden Breakdown Vehicle be.
One day, Isobella was commended by Miss Jenny for her hard work, so she was given the task of delivering a new shipment of tools for the Pack's Repair Shed. Max and Monty were very jealous, so they began to tease her constantly. Isobella was very upset and wanted to pay them out, but Kelly assured her that patience is a virtue, and that they would get their comeuppance soon enough from natural causes. Kelly surely hit the nail on the head when Monty crashes into a pile of rubble and damages his axels! Isobella, who is not aware of this recent development, returns home with a new assortment of tools, but is suddenly bashed into by Peter Sam and skids along the side of the level crossing. She is eventually brought back on the road empty trailered, worried if she will be in trouble for the accident. However, Miss Jenny tells Max and Monty that it serves them right, and will have to go about the tools for the time being. Isobella, after the days events, is now a firm believer in "serendipity!"
Isobella is very concerned about her appearance, trying to avoid mud and dust whenever possible in construction. She works hard too, and is close friends with Kelly the Crane. She often tries to keep the younger machines in line, and vows to get back at Max and Monty for their ceaseless antics!
- Season 1: Shepherd's Pie (cameo)
- Season 2: Breakdown Blues, Pigeon Hunting (cameo), Serendipity, Scot-free (cameo), Rosie (cameo), Mavis and the Tornado (cameo), James Goes on a Trip (cameo), Rock-Star (cameo), Pummeling Percy (cameo), Blunderbuss (cameo), Aura of Menace (cameo), Swashbuckler (cameo)
- Season 3: Culdee Fell (cameo), Derek and the Two Faced Engines (cameo), Ice Breaker (cameo), Chivalry is Dead (cameo)
- Web Clips: Mike and Frank Banter: SLOTLT, ScarletFire, and EE93's Return (cameo), Gina gives Percy some pointers - Meet the Characters! (cameo)