The costume collector, when it was available, would store three of your "costumes" or appearances that you could switch between. Now there are ready-made costumes at the Store that are put-on/take-off like the Collector.
you use it to save costumes and if you want to you have to buy it it is 250 credits you save up to 3 costumes and you click customize if you want to wear it.
no you can not.
in the store
The costume, like others at the Poptropica Store, has an effect built in, but will not change the play of any Poptropica island or game.
ther is n harry potter costume in poptropica, sorry. (it would be cool though!)
You Cant
You can buy the "phantom" costume in the Poptropica store, but it will not work on Spy Island to get past the guards. Get the Chameleon Suit from Professor Spyglass. (see related question)
I vampire meow
You buy it at the poptropica store
It is the fire man!!
any island
The jack'o'lantern is a costume, previously available in the Poptropica Store.