Faker didn't show up in a lot of MOTU fiction. Clearly the toy was a low budget solution to getting another figure on the shelves fast. So it stands to reason that not a lot of attention was paid to him afterwards. However Faker does appear in one episode of the classic cartoon. In it he's a near identical clone of He-Man causing trouble. This idea got revisited in 'The New Adventures of He-Man' with another near identical clone named He-Slave (no really).
Faker does have various comic appearances, including a mini-comic late in the line despite being one of the earlier toys. His origins range from evil robot clone to magically created clone to random member of the Evil Warriors. I do like the classics take on Faker, in which he's a failed robot duplicate of Prince Adam. Man-at-Arms thought it would be a good idea to have a fake Adam to stand in while He-Man was off on adventure. The robot didn't work out and ended up in the hands of the Evil Warriors and reprogrammed. The idea is to fool the people of Eternia that He-Man had went evil. Pretty standard evil clone stuff admittedly, but it works.
I mainly like Faker because of his colors. The blue contrasts with the orange in such a weirdly fun way. I've made my joke about Eternia being full of living Halloween decorations a million times before, and I'm going to make it again. It's most obvious in his Battle Armor variation. With it, Faker has an orange version of Skeletor's battle armor that makes you wonder why he wasn't a seasonal special edition. Despite the very basic nature of the toy, Faker is pretty popular and generally gets a good amount of merchandise. Which I'm sure Mattel is only to happy to produce.