Why duplicates

[IronKnees]

You should probably add a "delete button" for some items or maybe you should make the items unique received (eg:hairstyles) so you won't be able to choose the same reward twice. I'm giving you this suggestion because someday after leveling I pressed by mistake on a hairstyle that I've already had and I ended having a duplicate that can't be removed or used in any way .
Thank you for your time spent reading this , and I hope you'll take my suggestion into consideration.

[Shinkurex]

Hey Iron,

Thanks for the feedback... To help you with your mishap of choosing a hairstyle you already own, I advise you get in contact with feedback@musegames.com. They should be able to assist you with getting a different reward for you.

Clear Skies,
Shink

[Watchmaker]

This is partially deliberate: hats and costumes are dyeable, so having multiples that you can dye different colors is potentially important.

However, there are some cases where that clearly doesn't help and clarifying those is a worthwhile suggestion.

[Imagine]

I'm more sad that I bought a ship theme but unlocked it just a few days later when I hit a level