Yeah, but he's cartoony naked. Like, there's not even really a bulge there, much less a sheath. And no nipples (Weasyl's rules don't make a gender distinction on nipples, I think). So I think it's safely General Audience. It's really up to your judgement, but consider the following from the Ratings Guidelines (see bottom right of any Weasyl page):

[General] ... Non-detailed drawings of nudity (e.g. cartoons, animals, aliens, characters, etc.) is permissible. However, no appearances of genitalia, implied or otherwise. Minimal clothing such as underwear or bathing suits are permissible provided they do not meet the criteria for "Moderate" below.