If held by a Dragonite, the Dragoninite allows it to Mega Evolve into Mega Dragonite if its Trainer has a Key Stone. A Trainer can only have one Mega-Evolved Pokémon at any given moment.
A Dragoninite debuted in Friends as Two, Me and You, appearing when Ult Mega Evolved his Dragonite for the first time.
Trivia
The Dragoninite was the first Mega Stone introduced in Pokémon Legends: Z-A to appear in the animated series, debuting before its name had been officially revealed.
