This'll only be humorous to those who read comics, and of those, only those who are pretty aware of the Green Lantern history.
I like it when creators take tiny little potshots at their competition. In this case, the artist cleverly showed Nova from the Thing's point of view, making it look like Rich is actually speaking to the reader, like we're all in on the joke. Nice touch there.
And if you're not in on the joke, he's referring to Mogo, the Green Lantern that is also a sentient planet. I won't tell you why he's making the reference, though. You'll have to pick up the latest issue of Nova (#21, available as of yesterday in finer comic book shops across the country).
Listening to: Hoobastank - Gone Gone Gone