This clip is best understood as a generic train whistle effect rather than a quote from a specific movie, show or game. The phrase choo choo has long been used in English to imitate steam train sounds, especially in children's media and toy-train play. Online, that familiar imitation became a simple reaction and editing sound for anything that rolls in, travels across screen or arrives with comic timing. It stays popular because the meaning is immediate and the sound reads clearly even in short, busy edits.