NAKAYAN from Pixiv, inkbunny and Furaffinity happen to draw a bunch of burds on the beach, including my sweet Robbie, and he was wearing some cute red briefs
Check it out on Pixiv: http://www.pixiv.net/member_illust.php?mode=medium&illust_id=48585220
Inkbunny: https://inkbunny.net/submissionview.php?id=784710
and Furaffinity: http://www.furaffinity.net/view/15670386/

So i decided to draw it him wearing 'em myself, because why the hell not?