Diana is the third of the feline characters to appear, though the circumstances of her introduction vary. In the manga, she first appears when the Senshi travel to the 30th century in Act 18. There, she is revealed as the child of Luna and Artemis, and when the Senshi return to the 20th century in Act 23, she goes with them. In the anime, she does not appear until Episode 133 of the SuperS series, when the grey kitten suddenly jumps out of the bushes, calls Artemis her Daddy, and nuzzles up against him. Artemis is confused and horrified, while an infuriated Luna accuses him of an affair and scratches him across the face before running off. Only later is it revealed that Diana has come from the future.

Just as Luna and Artemis guide Usagi and Minako, Diana acts as a guardian to Chibiusa. She is very curious, eager to help, and deeply polite, always addressing Usagi and Mamoru with the Japanese honorific "-sama" and calling Chibiusa by her formal title, Small Lady. She is also able to help the Senshi on occasion, despite her youth, and often because of the knowledge she has gained in the future.

In both versions of the series, Diana has red eyes.

(Source: Wikipedia)