The Messenger is Sabotage Studio's 2D platformer in the vein of classics like Shinobi and Ninja Gaiden 2. And, if you've finished it already, it now has some free DLC accessible to anyone who has made it to the credits.
Picnic Panic is a vacation-themed collection of three new levels with new boss fights as well, set on on Voodkin Island. It seems kind of like an anime beach episode, and various characters from the base game will tag along with you on this new adventure. As the press release puts it, "keep your friends close, and your anemones closer."
To access Picnic Panic, make sure the DLC has downloaded and you're on a save file that's beaten the final boss. If you're on New Game +, you'll need to have unlocked the map. Either way, head over to the shop and find the pink neon palm tree sign to set off for Voodkin Island.