The tune itself is Lydia the Tattooed Lady, a novelty song performed by Groucho Marx in the 1939 film At the Circus. Decades later, Breaking Bad gave it a darker second life as the ringtone for Todd Alquist, the polite young associate of Walt and Jesse whose cheerful phone sound contrasted sharply with his violent actions. Fans clipped the ringtone, shared it as a notification sound and reused it in edits, keeping it popular because that contrast instantly recalls Todd and the show's unsettling tone.