Singing traceroute
A traceroute spells out lyrics from “Let It Snow” in the reverse-DNS names returned for each hop.

The public reverse DNS names of a route can turn a familiar command into a lyric display. This specimen also shows how the presentation can be changed for a season or event.
It has no special DNS record type or client. The surprise comes entirely from naming.
Primary source: https://www.youtube.com/watch?v=O03k0DV2m1k