There are already very good answers here, but in some other cases (not this in particular) using map could be the "only" solution.
Specially when we want to use regexps, other than the standard ones.
For this case it would look like this:
$('.myClass').filter(function(index, elem) {
var jElem = $(elem);
return jElem.closest('#Create').length > 0 ||
jElem.closest('#Edit').length > 0;
}).plugin(...);
As I said before, here this solution could be useless, but for further problems, is a very good option