Depends. Do you want Disney costumes? When DH and I went to Disneyland on our honeymoon over Halloween (back in 1995 ), we went to the party dressed as a doctor and a nurse (store bought costumes, blue/green scrubs and the typical white nurses dress). Totally comfortable.
Now if you want Disney, there are tons of options. Peter Pan and Tinker Bell, any of the Princesses and their Prince, Mickey and Minnie. Lots of options there.