dop·pel·gäng·er
/ˈdäpəlˌɡaNGər/
An apparition or double of a living person. Or, in this case "dog".
These people came all the way down from Corona (over a two hour drive!) because they saw Archie on the Ocean Beach MainStreet Association website's Dog Beach page. Who looks like their dog on the right in the photo below. Ever since then he's been dubbed the unofficial Dog beach mascot.