Henry is the large green tender engine from the Thomas the Tank Engine universe, created in The Railway Series books and popularised by the long-running Thomas & Friends television series. His whistle, like those of the other engines, became instantly recognisable to generations of viewers who grew up with the show. Clips of individual engine whistles are widely shared in Thomas fan communities, compilation videos and soundboard sites, where fans collect them for edits and memes. Henry's mellow tone keeps it popular for nostalgic railway content.