Winx Club (2004) : 8x25

While the Winx save Sky from the frozen lake, Icy meets the white fox: it turns out that Dyamond is the planet of the witch and that the fox is actually her sister Sapphire, transformed into an animal by a shaman witch that years before she arrived on Dyamond and froze everything. Since then, Icy has vowed to become a witch stronger than her and to break the spell. The white fox accompanies the Trix in the subsoil of Dyamond by the prime star, which however ends up in a tunnel, in which Sapphire slips to retrieve it. In an attempt to enlarge the opening with magic, Stormy causes a collapse of the vault, forcing the witches to escape and abandon the primary star; the latter, however, appreciating that Icy has rescued Sapphire instead of abandoning her to danger, hands herself over to the witch.