Sonic X is an animated television series, featuring video game hero Sonic the Hedgehog and loosely based on the storylines of the Sonic Adventure series, with partial elements of Sonic Battle as well. Its rated genres are: action, adventure, sci-fi and comedy. It was animated and produced in Japan by TMS Entertainment with the partnership of SEGA and Sonic Team. It was released in Japan in 2003; that same year, 4Kids Entertainment obtained the license in a joint effort between 4Kids and Viz Media (it was formerly with ShoPro Entertainment before ShoPro and Viz LLC merged into VIZ Media) & distributed by FUNimation. It is also broadcasted in Europe, Australia and New Zealand, Brazil and Latin America by Jetix, and in Canada by YTV.
Originally planned as a 52 episode series which would be inspired by the story-lines of the Sonic Adventure series, Sonic X had now expanded to 78 episodes which were shown in Thailand and France in February and March 2005 (was going to expand to 93). These additional episodes (53 to 78) were never aired in Japan. A very interesting feature about the anime is that the original Japanese version is probably one of the more controversial anime to come across 4Kids' line of dubbing.
Cosmo is a female child of a plant-like alien species whose homeworld was destroyed by the villainous Metarex. She is an ally of Sonic the Hedgehog and his friends, and it is widely accepted that her primary purpose in the series is that of a love interest for Tails, the two characters being of the same age and displaying an overt fondness for one another. After the attack, Cosmo escaped into a ship and arrived on Sonic's planet. Tails, Cream, and Amy were the first to find her, and they questioned her arrival. Cosmo told them that she was looking for the "legendary hero that can use the Chaos Emeralds, Sonic the Hedgehog." However, she refused to tell them any more. Later, while in Tails' jet, the X-Tornado, she spotted Sonic and hopped out to greet him. Cosmo pleaded for Sonic to help her.
Sonic agreed to help her and he, Cosmo, Tails, Knuckles, Amy, Cream, Cheese and Chris Thorndyke, who recently arrived on Sonic's world, began traveling through the universe in Tails' new space ship, the Blue Typhoon in search of the Chaos Emeralds which Sonic scattered through the universe during his first battle with Dark Oak.
Later in the series, Shadow boarded their ship and attempted to kill Cosmo, as he believed her to be a spy for the Metarex, but Cosmo's friends managed to keep her safe. Tails especially endeavored to keep her safe, to the point of almost being knocked unconscious. Before Shadow could do Cosmo any harm, a Metarex broke in and interrupted the fighting. Dark Oak called Cosmo "White Seed" and told her that she did a good job. Cosmo then remembered that before she escaped from her space colony, the Metarex were planning to use her as a spy.
Chris and Tails managed to locate an invisible signal and found that it was attached to her brain; if they had gotten rid of it, Cosmo's hearing and sight may have been lost in the process. In the English version Knuckles said that it would have been best to do that, but Tails refused to harm Cosmo. In the Japanese version, however, Knuckles yelled at Tails that there had to be a way to remove it without hurting Cosmo, to which Tails yelled back that he had no idea how to do both, assuming it was possible. Later, in the English version, Cosmo learned that she could hear the Metarex in her head and fell into deeper despair. While she was disheartened, Chris told Sonic that he now understood why Cosmo was able to understand the Metarex language.
In Episode 74, Cosmo tried to run away but was stopped by Tails. Their friends then showed up and said they were determined to defeat Dark Oak instead of risking Cosmo's hearing and sight. In Episode 77, Cosmo sacrificed herself by fusing herself with the Dark Oak planet to make it weaker so that Tails, Super Sonic and Super Shadow could destroy it and save the universe. At first, Tails refused to, but Cosmo convinced him that it was the only way to save the galaxy. Tails trusted Cosmo and ended up shooting her (in the Japanese dub, he yelled that he loved her while doing so) with the Sonic Driver (Sonic Power Cannon in the English dub), causing her to be killed in the process (in the ending credits, she says to Tails that she loves him, while in the dub she says she'll never forget him). According to the Japanese version, in an attempt to rescue Cosmo from death, Super Sonic and Super Shadow used Chaos Regeneration, but all they managed to produce was a small seed although in the English version, Chaos Regeneration is not used and Cosmo implies that the seed is her child. In episode 78, when Sonic arrived back on board the Blue Typhoon, he hands the seed to Tails, who collapsed with grief as he realized that Sonic was unable to save Cosmo. However, the seed sprouted in the end.