Articuno from the binoculars.
The Articuno binoculars cry glitch is a natural glitch confirmed in Pokémon Red, Green, and Pokémon Blue (Japanese) as well as German and possibly other localizations of Blue. It was documented by 80C and spread by ChickasaurusGL.
If one repeatedly view the Articuno in the binoculars on the second floor of the gate on Route 15 (east of Fuchsia City), there is a chance that the cry will distort the audio. On rare occasions the cry will sound like Nidoking; a Pokémon with the same base cry, $09.