Bluebell is Mrs Porty’s donkey and is one of Ivor's best friends. Even though she cannot talk, she and Ivor just enjoy sitting around together.
As the Merioneth and Llantisilly Rail Traction Company Limited has only one train engine (apart from the short service of Juggernaut), Bluebell is sometimes called upon to provide motive power. Examples include the towing by chain of the broken down engine Juggernaut and also the pulling of Mrs Porty's donkey cart when this has temporarily set on the railroad tracks to pursue 'robbers' when Ivor has been 'stolen' in the episode The Lost Engine; in this latter case, like a steam engine, Bluebell strictly observes the railroad signals, halting the chase until Owen the Signal has raised the signal arm.
Bluebell is very literal in her interpretation of instructions, and will follow them to the letter.
Ivor loves to pull his friend around the railway in her own carriage, but as you can imagine, Dai is not pleased, as it is not an appropriate use of railway resources.
When Ivor gets stuck, while a crane trying to pull him out topples over, followed by the fire engine getting stuck itself, Bluebell comes to the rescue by bringing back Bani and his elephants to help restore normality.
Dai Station is so grateful for the help Bluebell has provided, that he says that henceforth she can always have a ticket to ride on the railway. From that day on he has no problem with Ivor pulling her around on her donkey carriage.