Sigh.Yeah, uhm, I still donut geddit. Can someone please try to explain the joke in a way that doesn't not make sense? Thank you.
OK, lemme break it down for you: DC comics used to sublet it's characters to other publications. One of those was once a children's dictionary, you know the sort, where various different characters do different things to explain the meaning of words. For various reasons, the entry for the word "forty" became internet-famous and is now a meme in its own right. And Lex Luthor is still a very bad man.