If you haven't been following the whole new Blaster Master saga and have a penchant for retro games, you might want to listen up.
Inti Creates managed to wrangle the old Sunsoft license for the classic NES game (which in turn wasn't a big hit until it was localized and added a frog), and has been doing an amazing job so far of combining that retro feel with their own unique spin. There's two full games out at this point, and both of them have strings of DLC characters that are free for a limited time, then revert to paid add-ons.
Blaster Master Zero 2 is up, and Copen (a character from the Gunvolt universe) is free today to celebrate the release of the game on Steam. As is customary, you can head to the eShop listing on your Switch and download the Copen DLC for free when it's released. On Steam, you sadly need to own the game to acquire the DLC.
You have until December 12 of this year to pick Copen up before he becomes a premium download.