There's not really much explanation to go with this one. That's Cancer, from McFarlane Toys' spectacular failure Warriors of the Zodiac line, and Chemo, from DC Classics Series 9. Cancer, chemo, get it?
Okay, here's an unexpected fun fact: Chemo's "speech" is copied directly from an issue of Infinite Crisis - that's DC's official font.
And honestly, what's "GG" supposed to sound like, anyway? It's like in Grant Morrison's crappy JLA book, when he was constantly having Batman go "Hh." What the hell was that about? If you come up with a little onomatopoeic sound that only makes any damn sense if you explain it to people in person, your little onomatopoeic sound has failed.