This year's Pokemon GO Fest has a featured Mythical that was originally introduced in Generation V and the Unova region — Meloetta, a dual Psychic/Normal-type Pokemon.
Meloetta is known to have a beautiful singing voice, so it's no surprise it would be featured in an event themed around a musical competition. While it may appear to be female, it's classified as genderless, like most Mythicals and Legendaries. While a lot of details about this year's GO Fest are still under wraps, there is some information out there surrounding the Idol Pokemon itself.
Meloetta is Great in Battle
With a max CP of 4490, 250 Attack, 225 Defense, and 225 Stamina, Meloetta has some pretty solid stats for battling that are very comparable to many Legendaries. Its fast attacks will be Confusion and Quick Attack while the possible charged attacks will be Dazzling Gleam, Hyper Beam, Psyshock, and Thunderbolt. It resists Ghost and Psychic moves and be weak to Bug and Dark-type moves.
It's unclear so far how viable Meloetta will be in the GO Battle League, but with its stats and typing, it may see some use.
Meloetta Has Two Forms
Meloetta is a Mythical Pokemon with two forms - the main one that it always defaults to is called the Aria Form. The second one is more of a power-up phenomenon called the Pirouette Form. This form occurs in battle only, and turns Meloetta into a Normal/Fighting-type.
Here, its stats drastically change, with Attack going up to 269 and Defense lowering to 188. We don't exactly know how the game will execute the form switching mechanic yet but based on the way that it works for other Pokemon, the form will be available either as a second Pokemon or through accumulating a special set of candies.
It Is Event Exclusive
Aria Form Meloetta is going to be available as a research encounter reward, so if you want one, you'll have to purchase a ticket to participate in the event. Niantic has discounted the price to a third of what it was last year, so if there's any time to splurge, it's definitely now.
Besides that, the ticket will get you a multitude of other rewards and activities to participate in. The ticket is $4.99 USD, or the equivalent in your local currency. The ticket price is for the fifth anniversary of Pokemon GO, so it may not be the same next year.
It Will Most Likely Be Limited For Some Time
Meloetta is looking like it'll initially be an event-exclusive limited-time Pokemon that probably won't be available for some time after GO Fest ends. In the past, some Mythicals have been released for ticket-holders first, before becoming more widely available later.
Some Mythicals have appeared in raids as well, like Darkrai and Genesect. But, the small cute ones tend to be accumulated through Special Research quests, as was the case with Jirachi and Victini. However, if it does turn out to be limited, there may be a chance that it can come back for another event, such as an Unova one since that’s the generation it is from.
One Form Is Better Than The Other
If the forms have to be caught separately and you have to choose between them (which is unlikely, but you never know), your best bet will probably be to go with the Aria Form over the Pirouette Form because it’s more useful.
The Fighting-type pirouette Meloetta isn’t very high tier when it comes to general stats, so if you aren't a collector, it isn’t worth it.
It's Champion Material
For players who enjoy participating in the Master League, Meloetta Pirouette Form is a must because it can use moves like Ice Punch despite its typing, making it able to deal significant damage against powerful Dragons like Giratina and Garchomp.
Ice is also effective against Ground (making it doubly effective against Garchomp), Grass, and Flying, all of which are seen in the GO Battle League frequently.
Additionally, Meloetta gets STAB (Same-type Attack Bonus) on Hyper Beam, which is incredibly powerful.
No Signature Move
In the mainline games, Meloetta had a special move called Relic Song that was the catalyst for its transformation from Aria Form to Pirouette Form.
However, it doesn't seem like Meloetta will have access to this move on its initial release. This might be because Meloetta's other form will come at another time, making the move a bit awkward to have at the moment.
Even though Jirachi and Victini got their signature moves, neither of them have a second form, so they don't pose quite the same issue.