The line comes from asdfmovie, the long running animated sketch series by TomSka that built its humor on very short, random gags. The I Like Trains kid became one of its most quoted recurring bits, repeated across later episodes and endlessly clipped, remixed and reposted by fans. Its popularity comes from how self contained it is, with a setup and payoff in a few seconds that needs no context. That brevity helped it survive as a reaction sound long after the original sketches first spread online widely.
About this sound
The I Like Trains sound effect from asdfmovie, where a kid cheerfully says the line before a train crashes in for a classic meme punchline online.
This clip captures the deadpan asdfmovie gag built around a smiling kid who simply announces that he likes trains. His bright, innocent delivery lasts only a second before the joke lands with a loud train rushing through the scene. The contrast between the cheerful line and the sudden, absurd impact is what makes it funny. It works as an instant non sequitur, cutting away from normal conversation to pure cartoon chaos, and the short setup means viewers get the punchline before they have time to expect it at all.