After Mell gets kicked out of both Heaven and Hell (and after the "happy you have a body again" sex), Mell tells Caliban that since they've both been kicked out of both afterlives, whatever happens after they die, they'll face it together.
Mell's reaction when Artie was about to die.
All through the series, Zeta felt a connection to the main characters. As it turns out, she was right. Zeta was Helen's fifth-grade science fair project. They finally meet at the end of the next-to-last chapter.