The latest Vampire Survivors release is a straight-up crossover with Contra

Vampire Survivors continues to roll out new DLC in ever weirder, more delightful packages this month with Operation Guns, a full-on crossover between the worlds of Vampire Survivors and long-running shoot-em-up slash bullet hell slash action arcade series Contra. 

"Are you a bad enough Vampire Survivor to save the President's cousin's sister's dog from the traitor squadrons of Red Falcon?" asks the DLC description. Which I suppose is a legitimate question to ask in the context of Vampire...