Alfie is upset when Max and Monty tease him about his size at a demolition site by calling him "Small fry, and "Half pint." Thomas tells him it does not matter as long as he is useful. Later, when Oliver is demolishing a building, Alfie hears a noise inside and goes to investigate. He finds a cat and her three kittens and rescues them. The other machines cheered, even Max and Monty, and from then on Alfie never complained about being small.
According to storyboards by Robert Gauld-Galliers, Ned was originally going to play a larger role in helping Alfie save the cat and her kittens.
In the US release, Michael Brandon says "Meow! Meow!" even though meowing noises for the cats are audible in the background.
Oliver does not use a wrecking ball for the demolition. Instead he uses a scissor claw, which they did think of using for an alternative for when the wrecking ball did not work in Thomas' Trusty Friends.
Surely Thomas would have other jobs to do after taking Alfie to the demolition site.