Radical Smile is one of the three skins released under the monthly Dark Dimension Zone offer. It could be individually purchased with game coins in early May 2018.
Radical Smile could be purchased in the Skins Shop under the ‘Dark Zone’ tab for 1900 coins. This skin was available for a limited time and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.
Note: The Dark Dimension Zone offer with Radical Smile was released again for a limited time in late August 2019. The cost for Radical Smile remained the same at 1900 coins.