Super Smash Bros. Ultimate brings back almost every Pokémon stage from the series and features 33 Pokémon in Poké Balls and 24 in Master Balls. Here is the list, based on Poképédia.

Spear Pillar.

The Pokémon stages

StageOriginal game
Saffron CitySuper Smash Bros. (Nintendo 64)
Pokémon StadiumSuper Smash Bros. Melee
Spear PillarSuper Smash Bros. Brawl
Pokémon Stadium 2Super Smash Bros. Brawl
Prism TowerSuper Smash Bros. for Nintendo 3DS
Unova Pokémon LeagueSuper Smash Bros. for Nintendo 3DS
Kalos Pokémon LeagueSuper Smash Bros. for Wii U

Only Melee’s Poké Floats did not return. The details of the 2014 stages are in our guide to Super Smash Bros. for 3DS / Wii U.

The Pokémon in Poké Balls

Bewear.
Pyukumuku.
Abra.
PokémonMove
Raichu (Alolan)Stoked Sparksurfer
VulpixEmber
Vulpix (Alolan)Powder Snow
MeowthPay Day
AbraTeleport
ElectrodeExplosion
Exeggutor (Alolan)—
GoldeenSplash
StaryuSwift
DittoTransform
EeveeTackle
SnorlaxBody Slam
TogepiMetronome
BellossomGrass Whistle
ScizorMetal Claw
GardevoirReflect
MetagrossEarthquake
AbomasnowIcy Wind / Ice Punch
SnivyRazor Leaf
OshawottSurf
ZoroarkFury Swipes
ChespinSeed Bomb
FennekinIncinerate
FletchlingPeck
SpewpaStun Spore
GogoatTake Down
SwirlixCotton Spore
InkayTopsy-Turvy
DedenneDischarge
BewearBrutal Swing
PyukumukuInnards Out
TogedemaruZing Zap
MimikyuLet’s Snuggle Forever

The Pokémon in Master Balls

Darkrai.
Arceus.
PokémonMove
GoldeenSplash
MoltresFly
Mew—
EnteiFire Spin
SuicuneAurora Beam
LugiaAeroblast
Latias and LatiosSteel Wing
KyogreHydro Pump
DeoxysHyper Beam
PalkiaSpacial Rend
GiratinaDragon Breath
DarkraiDark Void
ArceusGravity
VictiniVictory Star
ZoroarkFury Swipes
KyuremGlaciate
KeldeoSecret Sword
MeloettaEchoed Voice
GenesectTechno Blast
XerneasGeomancy
Tapu KokoElectric Terrain
SolgaleoSunsteel Strike
LunalaMoongeist Beam
MarshadowSpectral Thief and Soul-Stealing 7-Star Strike