Hi,
The crown is definitely a different item from the mickey ears.
Difference:
The crown looks similar to what you would think of as a tiera. The mickey ears are exactly that: a little hat with mickey ears. When on, they basically look like this

.
More info on Ears
Ears come in black and gold. The gold are for the 50th anniversary. The black, as far as I know, are only available when a character is made at DLR or WDW, or of course, trade. (Someone correct me here iif I am wrong and they are available elsewhere.) Gold ears are also available at the parks. You can get them when you purchase a hat from one of many hat stores (specifics on this are listed in the sticky at the top of the main vmk message board).
At this time, the only way you can get black or gold ears in the game itself is by trade or gift.
Specialty Ears
Although I do not think this is at all what you are refering to - I will mention one other classification of ears, as if I do not, someone surely will.

There are some hats (princess hats, sorcerers hat) that have ears as well. I call these "specialty ears" but you get the idea.
Hope this helps (and, of course, if I am wrong or left something out, someone feel welcome to kindly correct me),
Disney Dreams / jegrezo