I completely missed this joke when I was younger

I don't get the joke

Mary Jane....Marijuana....I get it now!

Oh my god!!

But Mary Jane doesn't even sound like marijuana...

Well, isn't Mary Jane slang for Marijuana?

Wtf???

wat, i don't think that was a pun//or he's dumb//i think he liked the girl thats why he said it, disney/or sometihng/wouldn't do that i don't think

Shut up all of you did any of you take a damn health class how could you not get this

The joke is that Mary and Jane are 2 names, not 1.