>>118148632Gaz was completely naked, covered in a shiny layer of sweat, and POUNDING an equally naked Zim into the bed with every slow thrust, sending that awful PLAP echoing through the room. That whine that broke Dib's concentration came from Zim roughly grabbing her ass, leaving rosy streaks where his fingers were.
The three emotions running through Dib's mind - the embarrassment of walking in on a family member, the innocent curiosity of viewing a mating alien, and the primal disgust of ZIM HAVING SEX WITH HIS SISTER - threatened to overwhelm him.
"Just- just let me finish, Dib."
On the corner of the bed, Dib saw a bundle of rope, suggesting this encounter hadn't begun as an entirely consensual one. Clearly, that wasn't the case anymore, if Zim's legs locked around Gaz's waist were any indication. For a second, Dib wondered how she had even gotten him in here without him noticing, but put it out of his mind. As revolting as this was, Zim was still stuck inside Dib's house. Gaz could finish screwing him, and then Dib could murder him, and everything would be fine-
Zim got even louder as Gaz sped up, hilting herself with every thrust. With ragged breaths, Gaz leaned over so her face was inches from Zim's and, loud enough for Dib to hear, asked:
"Are you getting close, Zim? Do you wanna come inside me?"
Zim nodded desperately, grinding against Gaz harder. Gaz changed her pace - still rough, but so much slower - and caught his lips in a sloppy kiss.
"Beg for it."
Zim whined and gasped, and Gaz's hands slammed onto Zim's wrists.
"Come on, Zimmy baby. Tell Gaz what you want her to do."
At "Zimmy baby," Zim's red eyes widened, then crashed shut as his legs gripped her waist tightly.
"F-fuck me! Fuck me harder, Gaz!"
"Good boy." Gaz brought him into another messy kiss, and fucked her Zimmy baby harder until they were both screaming for release - Zim more loudly, of course - clutching each other as they careened over the edge together.