Thomas first appeared in The Railway Series books by Wilbert Awdry in the 1940s, before becoming the star of the television series Thomas & Friends, which began in 1984. The little blue tank engine and his cheerful whistle became familiar to generations of children through books, television and toys. Online, the whistle is now shared as a short sound effect and reused in memes, edits and reaction videos, where its instantly recognisable tone works as shorthand for a train, an arrival or a light-hearted railway joke.