User blog comment:Pikatwig/Sonic Timeline Theory/@comment-1986314-20120301132152

Including Sonic Underground in this timeline is ridiculous. As far as I'm concerned, it's not considered to take place in the game timeline, but rather in a different reality (which also applies for things like Archie Sonic, Sonic the Comic, and other TV shows). Also considering Robotnik's appearance in Underground, how could he lose weight so quickly?

On a side note for Sonic 1, I believe the Japanese manuals of the first few games state Sonic is 10-13, but the American ones say he's been 15 all along.