Were having a Sega mascot topic? Coooooooool.
Also being a Genesis Kid myself I had no idea who Professor Asobin was until now, I can't believe there is someone who is even more ignored then Alex Kidd!
God rest Segata Sanshiro's soul, He died in his last commercial, ironically the commercial being for his own game, and I mean the character not the actor, the actor however is Kamen Rider 1 (And still alive today :p)!!!
Also I don't think Ulala was a Sega mascot for the Dreamcast, sure she's forever a Sega Allstar and all but I think either the mascot was Sonic or the Dreamcast didn't have a mascot.
I think that's about it for mascots from Sega, Sonic's the main one now sence the Genesis, but if I may recommend Doc how about we list all of the Sega Allstars.
Joe Musashi (Shinobi Series)
Gillus Thunderhead (Golden Axe)
Robo and Mobo (The Bonaza Bros.)
Axel Stone and Blaze Fielding (The Streets of Rage series)
G (The House of the Dead)
Bug! (Bug! series, and yes I'm stretching this a bit)
Chuck D. Head (Decap Attack)
Ecco (Ecco the Dolphin series)
Akira (Virtua Fighter)
Dr. Daniel Caine/The Ooze (The Ooze)
Sketch Turner & Roadkill (The Comix Zone)
Chuchus (Chu Chu Rocket, Never played the game on the Dreamcast but I have it for the GBA)
Billy Hatcher (Billy Hatcher & The Giant Egg, Was I the only one to get this game when it came out?)
NiGHTS (NiGHTS Series, concidering it has a sequel it's safe to say it's a series now)
Hornet (Daytona USA)
Ryo Hazuki (Shenmue series, I really do got to play those games one day)
Crazy Taxi (Crazy Taxi series, I forgot the first characters name, so someone fill me in on that one.)
Amigo (Samba de Amigo series, LOVE this game on the Wii, feel really bad I never got it for the Dreamcast)
Beat (Jet Set Radio Series, I do have JSRF for the Xbox, but currently my 360 won't run the game, MOTHERF***ER)
You know what I can't list them all there are WAY too many characters Sega has when you start making a list, hell they rival in number even Nintendo, Capcom, and Namco almost! Which makes you think why the hell Sega doesn't bring a lot of these series back, okay some have gotten new rereleases and all but still with Daytona USA out now maybe we'll see these old favorites back once more, oh and I vote for Sonic & Sega Allstar Fighters.