In Level 3-17, after blasting yourself down past a set of two crushers, you will come to a split path with two scientists on each side. Going down the left path and activating the switch at the end will open a pit which will lead to a small laboratory featuring a creature contained inside of a tube. Destroying the tube will trigger a bonus cutscene featuring The Maw, the titular star of Twisted Pixel Games' first game released a few months earlier in 2009, getting sucked out into space as 'Splosion Man nearly gets sucked out himself before waving goodbye, and cutting to a shot of The Maw hungrily swimming after a suffocating scientist. This cutscene rewards you with an Xbox Achievement called "Eventual Destruction of a Galaxy".
Contributed by MehDeletingLater