From Sega Retro
Professor Asobin (アソビン教授) is a smartly dressed anthropomorphic rabbit who was the first unofficial mascot of Sega.
Although he never starred in a game of his own, Asobin gained attention by appearing in nearly every game manual of early SG-1000 software since the SG-1000's retail launch on July 15 1983. He was replaced briefly by a very similar, but less leporine Dr. Games in 1984, but reappeared for the new range of MyCard software in 1985 and also appeared in a number of early Sega Mark III games as well. Often on the second or third last page, Asobin offered advice to players that was usually helpful and specifically tailored for each game.
His last appearance giving advice was seen in the manual for Makai Retsuden (aka Kung Fu Kid) released on 17th May 1987. He continued to appear in manuals on the page describing the correct care and maintenance of cartridges and cards during the rest of the Mark III releases, although no longer provided his customary gameplay advice.
Professor Asobin bares more than a passing resemblance to the "White Rabbit" character in Lewis Carroll's classic children's story "Alice's Adventures in Wonderland", with a particular similarity to the popular characterisation depicted in Disney's 1951 animated version of the book "Alice in Wonderland." No information is known as to the origins of Asobin or why, or if, Sega chose to mimic these characteristics.
In the first release of Phantasy Star on Sega's Mark III, Professor Asobin appeared in the manual, no longer offering gaming tips, but providing information on the correct care of the Phantasy Star cartridge. He was brought back for the Phantasy Star Fukkokuban Sega Mega Drive rerelease, but only to promote a telephone help line. Scans of both versions of the manuals can be found in Sega Ages 2500 Series Vol. 32: Phantasy Star Complete Collection for the PlayStation 2.
Professor Asobin did in fact make a cameo appearance in Segagaga.
There has been at least one documented image of Prof. Asobin cosplay