*devs walk into forum to see how excited people are*
*read all the hate*
I for one dig the cameo.
It's also a nod at the only other (so far) successful Kickstarter game that's so far delivered the experience it promised (I'm looking right at you, MN9). Was it necessary? No, but cameos aren't by nature. Cameos are about having fun, just like other easter eggs they'll surely put in the game. If they also had Banjo-Kazooie cameo, that'd be a nice nod at their roots, but that depends on Microsoft, I'm sure (just saying "we're cool with that" doesn't make lending an IP automatic).
Besides, it's not like they tried to shove every indie character as NPCs in the game (Shantae, Commander Video, Meatboy, etc.)