Don't Let the Good Life Pass You By - S3-E8
Plot hole: When Janet and Michael visit Doug Forcett, they realise his lifestyle, like drinking his own urine and only eating lentils and radishes, is not the "blueprint" they imagined. However, Janet should already have known all of these details, due to knowing everything about everyone in the universe, so a) she could have told Michael this without visiting Doug, and b) she should not have been learning all this for the first time herself.
Answer: No, he is fictional. The joke is that, despite being handsome and charming, Larry Hemsworth is so overshadowed by his brothers that nobody else has heard of him and he feels like a failure.