Celebi can only be caught through a specific event in these games:
* The "Time Travel" Event: This involved a specific, limited-time event where players could receive a special item called the "GS Ball". Using this ball in the Ilex Forest area would allow them to encounter and catch Celebi.
Unfortunately, this event is long past, and there is no known method to trigger it again on original game cartridges.
What you might be thinking of:
* The "Beat Up" Glitch: This is a separate glitch that allows you to use the "Beat Up" move on multiple Pokémon at once. However, it's unrelated to catching Celebi.
* Catching Celebi in later games: In later generations like Ruby, Sapphire, and Emerald, there are different methods to obtain Celebi, including events and other means. However, these methods don't apply to the original Gold, Silver, and Crystal games.
So, to sum it up: There is no glitch involving Sneasel and Beat Up to catch Celebi in Gold, Silver, or Crystal. The only way to obtain Celebi in those games was through the "Time Travel" event, which is no longer available.