Cosmo

Cosmo is a plant-like character who first made her appearance in episode 53 of the anime Sonic X. Her home world was apparently destroyed by the Metarex, who planted a tracking device on her. She appears to have a role similar to Cream the Rabbit's, always getting captured and used as a shield by Dr. Eggman.

During her time with Sonic's group, she develops feelings for Tails, who in turn returns the feelings. Vector even went so far as to try and set them up.

Shadow and Rouge discover that Cosmo is unknowingly working for the Metarex under the codename of "White Seed". Shadow then boards the Blue Typhoon in order to kill her and knocks down anyone that stands in his way. Tails stands up against him to defend Cosmo.

In episode 77, she transforms into a "final state" with the shattering of the red amulet on her chest that was left to her by her mother Hertia. She goes to help Super Sonic and Super Shadow who are in the middle of battling Dark Oak. She is able to immobilize him and tells Tails to shoot him with the Sonic Driver. Doing this would also kill Cosmo. Of course Tails refuses to do so not wanting to harm Cosmo. But she eventually convinces him. She is killed along with Dark Oak; though the English version never states that she died and said that "She went to live with her mother".

Personality and Abilities
Cosmo in general has a gentle person and is very shy. She tends to have little confidence in her abilities and criticizes herself often. But she still cares deeply for her friends and will always stand up for them.

Cosmo is apparently very light. She can use the petals on her dress as a parachute to float. She also understands various alien languages. She is also the only one besides Hertia capable of harnessing the power of the red gemstone she wears.

Cosmo's super state is seen in Sonic X, the red amulet on her chest is her power source leading to her transformation into her super state.

Reception

 * Though she has an overall higher approval rating than Chris, she is still criticized by some fans, mainly Tails fans. This is mostly because she shows romantic interest in Tails. Some also feel that she "warped" Tails' personality. Some also note that Cosmo resembles both Lumina Flowlight and Void from Sonic Shuffle.