While Dave was at the bar, after his break up with Helen, lamenting about the fact that he will never have lesbian sex again, a blond girl with glasses sitting next to him looked baffled and disturbed. Later on, it was revealed that the blond girl is his daughter from the future. There may be another layer to it, too: how would you feel if you traveled back in time and then overheard your dad lamenting a recent breakup with your mom?
Final exchange:
The "I Love You." "Not Enough." exchange volleyed between Helen and Dave has a bit of extra significance to it beyond the obvious paradox. When Dave hears it first, Brain!Helen was stating that after he went mad, he didn't love her enough to rein himself in, which she had for him for the longest time. When Helen hears it first, AI!Dave was stating that Helen didn't love him enough to let him go before it was too late. Both are applicable, if callous.
There's another level that the exchange works on. When Helen and Dave say "Not enough", they're also saying that the other person loving them isn't enough to make up for what they've done. Helen loves Dave, but that doesn't change the fact that she lied to him and experimented on him covertly for years. Dave loves Helen, but that doesn't change the fact that he failed to trust her and tried to kill her.
While Sunday pages were normally reserved for fillers and fan art, the last Sunday of each year had "Little Dave in Slumberland". Firstly, this was an Affectionate Parody of the classic Little Nemo comic strip; secondly, when re-reading the archives, you realize that Dave's dreams are foreshadowing events that will occur in the strip in the upcoming year. This occasionally serves as Nightmare Fuel, such as dream-Helen's comment, "I am just barely ahead."
Slight, but both Helen and Dave quote Alice's Adventures in Wonderland as they go mad, that is, as they (figuratively) leave the normal world and go into the land of the crazy, where anything is possible.
Pretty much the entirety of Mad Genius. The truly Mad are so wildly intelligent that they can extrapolate the future with immense accuracy, they possess the capacity to build a device capable of allowing travel between dimensions out of the parts of kitchen appliances that aren't even plugged in and the only reason they haven't successfully taken over the world is that they still possess enough human decency to feign charming incompetence because that's at least the better alternative to being left alone in their own mind.
Madblood: "I know what you're going through you know. The inside of your head is much bigger than you could ever have imagined, and you're worried you may never find your way out. I may as well spoil the suspense: you won't. What you are now, Mister Davenport, is what you will be forevermore: lost in the storm."
Afterwards he attempts (it's too late...) a Mercy Kill, remarking "he would do the same for me". Reflect on that for a moment.
strip suggests that a mad person's Genius Ditz and Cloudcuckoolander tendencies are all a front for their friends' benefit (especially combined with the writer's commentary, which notes that the audience never actually saw "the real Helen"), while the newly mad Dave reminisces in the November/29/2006