You don't expect that a movie that purports to be a silly comedy about the end of the world happening to the "real" Seth Rogen, James Franco, Jonah Hill, Danny McBride, Craig Robinson and Jay Baruchel to have poignancy or a satirical message, but that is what you actually get here. As the directorial debut for Rogen and long-time collaborator Evan Goldberg, they really put the work into this. A 30 million dollar flick that looks bigger and bolder than it does, though weirder than you'd expect at times. Mostly, it's full of gross-out gags and tasteless jokes.
But why then does it work so well, as a laugh-a-minute (even more sometimes) comedy that, up to a point, even takes it characters seriously? Because the actors have, naturally a rapore, and don't mind making knuckleheads of themselves. It's also an example of dumb being done smart, which can also be seen in Superbad and Knocked up and up to a point in The Green Hornet (The Interview, their follow-up, is even bolder and mostly works as well).
Celebrity culture can be easy to lampoon, but the targets here are not exactly obscure or in-jokey, at least too much. When McBride shows up, practically unnanounced, eating all of the character's stashed-away-for-the-duration food at Franco's place and proceeds to mock them mercilessly, every line is a zinger and is funny even if you don't know (by some chance) that Hill got nominated for an Oscar for Moneyball. Rogen and Golderg rely on the character's behavior, and a knowingness that the characters do dumb things.
The difference in quality between this and more super-low-brow stuff - let's say the Scary Movies flicks - is in the timing and quick-witted sponteneity and the embracing of the crude humor. When a demon shows up with a big swinging, uh, phallus, it certainly isn't subtle. But if just reading that you chuckle, then you know what you're in for. The actors are all game for being made jokes out of one another, and recognizing their idiocy especially in the back-drop that is presented here. And it's a real MOVIE as well, the filmmakers take the back-drop seriously and present it not as a joke - it can be rather terrifying to see some of the crazy things happen around these character (rapturing, holes in the ground sucking people in, fires, demons, crazy CGI creatures).
Ultimately, This is the End is all in good fun, revels in the ups-and-downs of these characters and their conflicts that bring them down to base levels, and the mockery is knowing and clever. It's also stylish and fun, and shows young filmmakers really strapping in and taking people for a ride. It's the kind of flick you can watch over and over. Especially if you have been aching to see PIneapple Express 2 featuring Woody Harrelson.