WMG / Todd Allison & the Petunia Violet

Violet is some sort of spirit or mind control entity that takes over people's bodies
Eventually, something will happen that will cause the entity to posses/control Petunia, adding an extra serving of drama. (Note: By mind control entity I mean a personality that is written over someone's existing personality)

Todd will get a relapse of TB
He's never been a healthy person. And it's happened before.

Cyril will become increasingly forward with his feelings for Petunia
This will lead to a Heartwarming Moment before Cyril is either redeemed by his love for her, enticed into corrupting her, or driven mad by his unrequited love until he decides to try and kill her. This is all probably a stretch considering how non-romantic this comic has been thus far, but then that's why its a WMG.

Todd is trying to find the cure for tuberculosis.
Well he certainly would have a reason to be doing so, seeing as how it's been plaguing his life and all.

There is no Violet after all, it's just Elijah in drag.

Violet is Aunt Harriet
For a long time I subscribed to the Violet=Elijah theory (not long after he was introduced, in fact), considering his dark behavior that's only gotten more suspicious as of late. Many people seem to be guessing it's Elijah at this point, but it hasn't sat right with me for a while...it feels more as if his [potentially] being Violet is a Red Herring to distract from stranger plot points (not to say they have to do with only Violet, considering the expansion since, but there has been a build up of events and conversations that haven't yet been fully explained to the audience).

Then, while comparing Violet, Petunia and Elijah, I realized three things: one, those who think Elijah is Violet will say he's wearing a wig, but...Violet's eyebrows are the same dark purple as her hair. Two: while later Art Evolution stops differentiating as much, the way Elijah's chin is drawn in early chapters is sharper than Violet's; maybe cosmetics could do something about that if Elijah felt the need, though, I suppose. And three, when checking between characters, I realized that Aunt Harriet has the same under-lashes. And lipstick. In the end, if Petunia could travel all the way to Melbourne without telling Elijah, why couldn't anyone else in their family do the same...? And since we don't see them past flashbacks, they have plenty of time to dye their hair convincingly enough to hide within Melbourne, for whatever reason it is that they feel the need to do so.

A variant that's possible at least a part of Elijah and Petunia's family is involved in a greater conspiracy; Aunt Harriet could be helping Elijah out by doing the dirty work he needs done in the same way Elijah has Cyril hired on. Or maybe it is Elijah in drag after all, but given make-up tips by Aunt Harriet, since the thickness of the eyebrows and bridge of the nose doesn't quite match hers... Or third, wildest guess of a variant: Aunt Harriet has a kid, a cousin who shares a particular resemblance with him...