>an element of a culture or system of behavior that may be considered to be passed from one individual to another by nongenetic means, especially imitation.
A popular idea, such as Marisa's over-reliance on the mini-hakkero, which is spread through a digital medium from person to person can be defined as a meme, yes.
>you mean non canon stuff?
Elements of PC98 have reemerged time and time again, and whether or not you believe it to actually be canon, it's undeniable that it has influence over the modern canon in implicit ways. As such, completely discarding it is foolish.