Invader Zim #27
On a search for the rare element Splodium-235, ZIM discovers that deep beneath his own base lies another alien base. And inside it is another alien. And this alien claims he took over the Earth years ago. Is he insane? More importantly, can ZIM steal his supply of Splodium-235 and get out? Or will he keep ZIM in his base forever because... well... he's just so lonely down there?