After reconciling and getting back together, Spamton wants to do something nice for Tenna so he volunteers to bottom. Tenna is concerned because of their size difference and Spamton is even smaller than he used to be. But they eventually do it anyways
Except it goes poorly, Tenna can't fit the whole thing in and Spamton's in agony feeling like he's gonna be seeing those pearly gates from the penetration alone.
So they stop. Spamton feeling bruised all over internally and Tenna crying into his hands feeling awful about the whole ordeal.