Rundown of my logic:
In the episode linked above, GIR Goes Crazy and Stuff, Zim, tired of GIR's chaotic and unhelpful activity, cranks his duty setting all the way up, making him an unstoppable robot invasion machine. GIR quickly realizes Zim is an incompetent invader, and leaves to go the library and learn everything he can about Earth so he can conquer it himself. Zim has to face him (along with Squidman) and find a way to deactivate GIR himself. GIR's refrain: "The mission is stupid. The master is stupid."
I think that something happened in the game, either by action at night or by losing Zim to Tak, that turned GIR to duty mode. I think he is telling us the truth about his night actions, but that they are not what they seem. Make waffles is pretty easily confirmed by the story, but "revenge" definitely seems like he went after Tak. And "luuk for pig-eee" is cutting into Membrane again. I believe that the names stayed innocuous, but the actions were sinister, reflecting his transition to Duty GIR. I believe he has taken over for Zim, and his mission is to destroy Earth.