Ray is a Mii from the Wii.
Ray originally appeared as one of the 65 Miis to be included with Wii Fit. Since then, he's appeared in Wii Fit, Wii Fit Plus, and Wii Fit U. In all of these games, his internal ID is 060. His Mii data filename is mii_060.rsd in Wii Fit and Wii Fit Plus, and mii_060.ffsd in Wii Fit U. He always appears in the game as the coach for the Rhythm Boxing game, and doesn't appear anywhere else in the game.
He has a creator name set to たかむら ("Takamura"). His birthday is set to August 8th and he has Mingling turned off. His Mii name in his Mii data file is レイ. His height is set to 107, and his build is set to 55. He is set to be favorited. In his Wii U/3DS-format Mii data file, he was originally created on a Wii (1).
His Mii data file contains unused data. His hair type is symmetrical and normally does not allow flipping, but his hair is set to be flipped anyways.
Ray is one of the few Miis to not only have an official voice actor, but to speak in full sentences. You can find a download of all of Ray's voice clips extracted from the game here. His North American English voice actor is Steve Heinke, who I was able to ask various questions about his voice roles in the Wii Fit series in this Wii Facts Plus post. At the end of the emails, Steve Heinke recorded a small clip thanking "Wii Fit sleuths" like myself, and Ray makes an appearance at the end of the clip. You can view a subtitled video of the clip below. (Remember: Steve Heinke only provided the audio file, while the visuals were made by myself.)
His name never appears in-game or in any official text. The name "Ray" comes from his Mii data file. Additionally, the name "Takamura" as the creator name implies that the person who made Ray is Jun Takamura, who is listed in the Wii Fit Staff Credits as a field designer.
Ray unfortunately does not appear in any promo art released. However, there are some rare cases where he can be found.
The Rhythm Boxing game can be seen in the bottom right corner of the NTSC Wii Fit + Wii Balance Board bundle box.