Yeah, it is me who is missing the joke.
It's a slow morning so I'm going to assume you're not trolling and you really don't get it. I admit that it's a bit hard to pick up on the subtle nuances of the humor when the phrase is written rather than spoken so lets close our eyes, and imagine that you're in a room, say a workplace and there's more people there than just the intended "victim" which increases the effect. Especially if the spectators have already been the brunt of this joke.
It's even better if you're experiencing the first snow storm of the year. You say to them something along the lines of "this time around we're expecting snew. That's right, "snew" not snow. Then you wait for the person to take the bait and ask you what's snew so you can say "not much what's snew with you". They feel a bit foolish, other people laugh and feel superior and then you go about your day.
If that doesn't make any sense to you, let's try another one that is similar in context.
Let's play a game! You close your eyes and I rummage around the house and find an object to stick up your ass and you try to figure out what it is. Ok, here we go. Close your eyes! I disappear for a few minutes, come back and shove an object up your ass. You say "oh that's a broom!". I say...no, but very close it's that metal rod that you use to move logs around in the fireplace, it's called a.. damn I forget what it's called.. give me a minute... geez I can't remember the name....