After finishing Green Hill Zone as modern Sonic in the original game, Sonic will mention to Tails that the area seems awfully familiar, with Tails saying "not to me." Green Hill Zone was from Sonic 1, while Tails didn't come into the series until Sonic 2, meaning Tails would have no memory of the area. In Sonic X Shadow Generations, this cutscene was completely re-recorded by the original voice cast to removed this reference by having both Sonic and Tails be familiar with Green Hill Zone and mentioning South Island, the main setting of Sonic 1.