From my original thread on Twitter

This is a continuation of an old topic Sonic CD placement in timeline, the fourth part to be precise or a 2.0 where brings together the topics of the other parts In the link here below you will find the topic in all its parts, however I will make a summary here anyway

In an old interview, Yamaguchi stated with great certainty that Sonic CD takes place chronologically between Sonic 1 and Sonic 2 but...

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...in this private chat (not mine) with Ohshima, the latter clearly states that Metal Sonic is an advanced version of Mecha Sonic, thus contradicting Yamaguchi's statement.

This contradiction will be further confirmed by Nishimura, where he states that Yamaguchi's statement contains a contradiction since Metal Sonic is more advanced than Mecha Sonic, thus confirming Ohshima's words.

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Now let's go back in time to the time of the development of CD and S2, always according to Nishimura, the latter seems to be surprised when it was known at the time of the existence of Mecha Sonic, so likely that during the developments CD was really thought of as an interquel.

But... it didn't seem in its case, in an interview Ohshima stated that Sonic CD was developed without having pressure to be any kind of sequel, basically a standalone title; So, going by hypothesis, the problem arose with the addition of Mecha Sonic in Sonic 2.

It would seem that at that time the Sonic CD team took into account the continuity of the series and they would have rightly thought that Metal Sonic is more advanced than Mecha Sonic, but Yamaguchi seems to think otherwise or at least ignored the robot in favor of his fox.

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Both Nishimura and Ohshima didn't mention Sonic 4, probably they had no interest in that project (how can I blame them...?); but this game seems to have ''fixed'' this misunderstanding between the members of the old team with a retcon.

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Sonic 4 seems to follow Ohshima's vision, stating that Sonic CD has no precise point in the timeline given its non-pressure of being a sequel to a game and placing Sonic CD as events prior to Sonic 4 but not necessarily directly prior to the latter; combining this with Metal Sonic as an advanced form of Mecha Sonic, Sonic CD would seem to precisely have a retcon placing it at an imprecise point between Sonic 3 & Knuckles and Sonic 4 (obviously because there are other games in between wink wink).

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