According to dataminers.

If you participated in the open beta of Ninjala, you might have noticed the bubblegum shooter’s emphasis on fashion. You can dress up your character and customise their physical features. With this in mind, Switch dataminers LeanYoshi and OatmealDome have discovered evidence of a special collaborative event potentially coming to the game.

Assuming this is the real deal, there’ll be cosmetic items such as masks, clothing, and even stickers. Again, there’s no guarantee, but if you’re a Sonic the Hedgehog fan and it does happen, it might be one extra reason to try out this game.

Read the full article on nintendolife.com

Original source: http://www.nintendolife.com/news/2020/04/sonic_the_hedgehog_might_be_teaming_up_with_ninjala