The achievement name "Paradise Found" is a parody of the 17th Century poem "Paradise Lost" by John Milton. When Sonic achieves a Good Future in any of the zones (via destroying the Metal Sonic projectors and roboticizers), he is essentially "founding" a paradise for the future of that zone.

There's an extra special stage that can be accessed through the sound test menu by setting all the 3 selections to 07. According to a former Sega Europe QA Tester, an extra Time Stone was to be collectible here. When collected in addition to the previous Time Stones, "S" TV monitors would appear where the ring TVs were previously located. When broken, Sonic would morph into a lesser version of Super Sonic, which would simply grant invincibility and greater speed. Graphics would not change.

In the XBLA/PSN version, the achievement for time travelling for the first time is called "88 Miles Per Hour", a reference to Back to the Future.

The Japanese/European soundtrack for the game is different compared to the American version. An example of this would be the intro and ending songs. In the Japanese version, the intro song is "You Can Do Anything" while the ending song is "Believe In Yourself" by Cosmic Eternity. In the American version, both the intro and ending songs are "Sonic Boom" by Pastiche. Because the American version got a new soundtrack and the intro and ending FMV sequences were being re-edited to fit in time with the respective music, the game was delayed a few months.

In the instruction manual of the original US release, Amy Rose was referred to as "Princess Sally." This was possibly done as a way to try to connect the game to the then-airing cartoon, but all references to Sally have been removed in re-releases of the game.

When Sonic CD was being remade using Christian Whitehead's self-made engine, he wanted to include a new level called "Desert Dazzle". However, SEGA thought it was a bad idea to deviate from the original project. You can actually find a concept image with Christian's initials on it in the sound test by entering PCM:32|DA:8

In the sound test if you enter this combination:



A message in Japanese will show up with creepy sonic heads in the background. The message translates to "Fun is infinite with Sega Enterprises. - Majin".

Sonic CD was originally going to be a CD enhanced version of Sonic 2, but after Sonic 2's release, it evolved into its own title. It was also titled "Super Sonic" early in development.

Standing still for 3 minutes will cause Sonic to jump off screen, saying "I'm outta here!" and cause an instant game over, regardless of how many lives you may have.

All level titles in Sonic CD are alliterations.

In Sonic CD, a DJ scene and a Batman tribute image can be brought up in the game sound test area by entering the following codes respectively:

FM NO.42 PCM NO.03 DA NO.01
FM NO.42 PCM NO.04 DA NO.21