Either Hal Jordan needs glasses, or he needs to pay more attention during his next trip through the reptile house at the zoo:
Uhhh ... Well, gosh, I might be wrong, Hal, but that looks an awful lot like a giant iguana. A giant purple iguana.
Okay, in all fairness to Hal, he IS supposed to be fearless. So, to him, maybe a giant purple iguana that's thinking about biting his head off doesn't qualify as a "fantastic danger." Still--! Maybe fearless really is just another word for stupid. Or maybe he figures that a giant purple iguana isn't much of a threat compared to other giant purple monsters he's faced.