Alkylation is a term in organic chemistry which means to form a carbon-carbon bond (simplifying, but accurate enough). This is actually somewhat difficult to do - it turns out that carbons are actually quite stable. For context, organic chemistry tends to work with a carbon "core" that doesn't really change a ton, with a bunch of random other atoms stuck on the carbon core. And you typically mess with the other random atoms rather than the carbon core.

However, in some semi-specific cases, you can manipulate a molecule to be unstable enough that it would be willing to break or form carbon bonds. Many forms of alkylation involve using a second molecule that contains a carbon bonded to a bromine or iodine (in this case, the molecule is C2H5Br). The end result is that your molecule (the one you want to modify) kicks out the other molecule's bromine, and a new carbon-carbon bond is formed in its place. Basically, you've just fused the two molecules together.

The meme is just showing several examples of C2H5Br being used as the "secondary molecule" and being fused onto things that make zero sense.

Edit: ironically, the last example ("alkylating agent itself"), despite sounding the most absurd, is actually probably the most feasible example to alkylate

I read this meme as a satire on the nature of graduate school research projects, where you often spend inordinate amounts of time repeating the same type of experiment in a variety of ways. This lets you publish either on the sheer body of work or, ideally, one of the products is particularly interesting and you get a bigger paper from it alone.

The "substrates" in this meme are odd and difficult to react, which again reflects many thesis projects. Also there are no stated goals and success is hard to measure or define.

Despite the absurdity of the scientific work, the subject still chooses to perform it even though they are deprived of real world relationships formed at Susan's baby shower and may also directly degrade their relationships with their Mom, brother's girlfriend, and dog because of it while also putting their health in jeopardy via cell alkylation.

It's crudely drawn images of an alkylating agent stuck to shit. I'm gonna go out on a limb and say that's the whole joke. Like, no deep levels to this. I think it's literally what you see.

Uh, well to alkylate something is to make it more alkaline, that is to make it less acidic.

In the case of the girlfriend, I believe the joke is that the OP fucked her, since the vagina is very slightly acidic and semen is more alkaline. The others are just nonsense to me.

Mind you, all of that’s a giant shot in the dark. I work in electronics, not chemistry.