It's not really Apatow-related, but I can understand the label. Seth Rogen would be in it with him. Hell, Craig Robertson would be in it, too, and I don't think he's ever even done an Apatow flick. Then expand it to Rogen's writing buddy, Evan Goldberg. And Jay Baruchel, who also writes, IIRC (think he did 'Goon,' possibly with Goldberg?). You can eventually end up with a lot of flicks that share styles and tones and a big cast of characters that intermingle a lot.
Kind of just the next generation or an expansion of the 'frat pack,' after Will Ferrell, Luke Wilson, Owen Wilson...I think they even lump Jack Black and Ben Stiller in there.
Basically, comedy has become very 'ensemble.' And that ensemble doesn't typically change a whole lot. Everybody's one degree from Judd Apatow. Or hell, Wes Anderson.