You know, the whole every Rick has a Morty thing made my mind wake up at 2 am just to question why, and my brain came up with this:
What If Rick is so dependent on Morty because he is like a multiversal constant in his life?
Like Rick is aware that the multiverse is a shit hole with unpredictable circumstances thrown around every corner. He is possibly jaded with his entire exsistance and has seen, visited, and possibly destroyed alternate realities of himself.
Morty points out in “Close Rick-counters in the Rick kind” that their relationship must be something special to span across multiple time lines. Of course Rick replied with the genius waves and “morty” waves, but that is debatable. It is implied that the “morty” waves is code for being an idiot or just dumb. If Rick needed to mask his intelligence by standing next to someone dumb, Jerry certainly fits the bill.
Okay well there is many reasons Rick doesn’t bring Jerry, mostly because he’s annoying. Okay well what about Summer? In the episode “A Rickle in Time” Rick educates Summer and Morty how much of a pain in the ass they are. The joke starts that he can prove it mathematically. And I, being obsessed with this show, noticed that there was a wavelength graph on the nonsensical whiteboard of Rick doing a proof. I believe if Rick wanted to graph how much of a piece of shit they are, a simple bar graph would suffice. However, I think the wavelength graph showed both Summer and Morty’s brainwaves. Rick said that Summer and Morty are identical in this aspect. Rick also said something along the lines that his distinct frequency of his brainwaves (due to his genius) is easily traceable (Close Rick counters). If Morty’s brainwaves is complementary, in turn, according to the episode “a Rickle in Time”, so is Summer’s. So it begs the question, why not take Summer? He has in some episodes, but still favors Morty. If Rick truly just needed a camouflage, it shouldn’t really matter which grandchild he brings. Note: it would be just as easy to get any random idiot walking down the street in any planet. In turn, he has a human shield he doesn’t have to protect, care for, or have any attachment to. Like a one night stand, grab a person, do the deed, leave.
Which finally bring me to my theory: Morty is a multiversal constant in Rick’s life. Rick has been to many planets, dimensions, timelines, etc. And he always has a Morty as a grandchild. In the infinite timelines of the many Ricks and Mortys, they are always paired up. This suggest that Beth, Jerry, Summer and whoever was Rick’s wife are not constants, or at least, not as much as Morty.
Let’s take it back to Rick’s wife. Who/whatever Rick fucks, he impregnates her and he has a child. That child ends up being a “Beth”. That child marries, possibly a “Jerry”, and they have a child. Note this child doesnt necessarily mean it’s a “Summer”. In the episode “Rixty minutes” Beth had the choice and either succeeded or failed to have the abortion. It’s possible in an alternate timeline, Beth succeeded with the abortion and Rick came back to Beth’s life, there was no Summer, but there was a Morty.
I also said whatever in terms of Rick’s wife because of his relationship with Unity. Rick had a memorable relationship with Unity and since she can assimilate any species, its possible Rick fucked an alien. This can be proven in Pocket Mortys with Mortaion Morty, Exo Morty, etc. With this Rick’s “wife” is a mere variable whose sole purpose is to make a “Beth”.
I assume Rick came back to his family because he wants a constant in his life when his life was too unpredictable for him. And based on his interactions with his family, he has a preference who to cling onto:
This could possibly explain why Rick would go above and beyond to save Morty and why he has such a “irrational attachment” (Rest and Riclaxation) to Morty. It’s the reason why he saved Morty in the Cronenberg universe and not all his family. He is obsessed to have at least one thing familiar in such an unpredictable universe. And the only thing that can be considered a constant to a Rick is a Morty.
But that’s just a theory.