There are two schools of Micheladas. One is with beer, lime juice, and Tabasco/Worcestershire sauce with a salted rim. That's the one I've most often read about and had in several bars in California and even in Mexico.
The other type is this one, a beer Bloody Mary. I've only read about it but obviously it's popular enough that they produced a pre-mixed product and already test-marketed it before launch.
And apparently, it's already available in my closest Mexican grocery. I'd try it except I don't eat meat. Maybe I'll experiment with V8 juice instead.