Niantic has announced that XXS and XXL Pokémon have been added to Pokémon GO and that there are new celebratory message for breaking records.

New Pokémon sizes have been discovered in Pokémon GO!

Trainers,
Time to break out the scales—Trainers have recently discovered XXS and XXL Pokémon!

Pokémon such as Poochyena, Mightyena, and Mawile have recently been observed in these sizes, and your Pokédex has been updated to start tracking the sizes of the Pokémon that you catch. We wonder if other Pokémon may have undiscovered sizes as well!

Keep a sharp eye out, Trainers. Will you try to find these elusive Pokémon and update the records in your Pokédex? Let’s GO!

More sizes of Pokémon are appearing in Pokémon GO!

Trainers around the world have encountered Pokémon in previously undiscovered sizes—XXS and XXL. These sizes have been observed in the following Pokémon so far.


: If you’re lucky, you might encounter a Shiny one!

New encounter animations

When you encounter an XXS or XXL Pokémon, you may notice that things look a little different.

Visible size variation!

XXL and XXS Pokémon are visually larger or smaller than their standard sizes when you observe them in an encounter or adventure with them as your buddy.

Sizes will now be tracked in the Pokédex

Once you catch at least three of any one Pokémon, your Pokédex will begin to showcase your records for the largest, smallest, heaviest, and lightest specimens that you have caught.

New celebratory message for breaking records!

Trainers who catch XXS or XXL Pokémon—or find smaller XS or XL-sized Pokémon than they caught previously—can enjoy a new celebratory message when they break their record. Trainers need to catch at least three of any particular Pokémon to set a record for that Pokémon.


Source: https://pokemongolive.com/en/post/different-sized-pokemon-in-pokemon-go-xxl-xxs/