Greninja

A habitat matching this ambience raises Comfy Level faster. Time and weather gate whether a Pokémon turns up at a habitat at all — though light overrides the clock: a night Pokémon spawns at any hour if its habitat sits somewhere dark such as a cave or underground, and a day Pokémon spawns at night if its habitat is ringed with light.

Give or place anything matching these and both friendship and Comfy Level rise much faster — a matching item lays down with a bigger sparkle. For a Pokémon with the Trade specialty, matching items are also worth 50% more on the scale.

1 Lots of water

30+ items

Resort hammockTable settingPaper Party cupsSoda floatShaved iceModern sinkToiletSinkBathtime setCleaning suppliesShowerBathtubBouncy blue bathtubHumidifierFunky diffuserWater basinCanoeInflatable boatBeach parasolHorsea fountainFire hydrantSprinklerMystic WaterWater pillar quarterHoppip water bottleJuice trioTeaware setBottled shipGyarados fountainBubble machine

2 Ocean vibes

35+ items

Resort stoolResort chairResort sofaResort bedDeck chairBeach chairResort hammockShip's WheelSandboxInflatable boatBeach parasolHorsea fountainFishing rodHarbor streetlightShell lampResort lightMarine chestMarine closetMarine tableOrnate standMarine chairOrnate chairMarine sofaMarine dresserBottled shipDecorative Dive BallDecorative Lure BallWindup InkaySand toysPrimarina statuePearl streetlightSand bedSwim ringBig swim ringBeach volleyball set

3 Cleanliness

14+ items

Waterproof seatLarge mirrorModern sinkWashing machineToiletSinkTowel rackBathtime setCleaning suppliesShowerBathtubBouncy blue bathtubWater basinCooler

4 Shiny stuff

77+ items

Crystal fragmentStardustGaming fridgeGaming chairGaming bedMunna bankBathtime setCleaning suppliesTabletCell phoneLaptopComputerGaming PCTelevisionWall monitorCrystal ballTabletop micStanding micGold TeethBig NuggetAuspicious ArmorClear BellGym emblem statueSpacesuitModel space shuttleBellSignpostInformation boardRaichu signFire hydrantMini generatorMushroom streetlightChic streetlightPoké Ball lightPoké Ball lampRed meteor lampOrange meteor lampYellow meteor lampGreen meteor lampBlue meteor lampIndigo meteor lampViolet meteor lampMirror ballFluorescent lightGaming lightString lightsMusic mat (low do)Music mat (Re)Music mat (Mi)Music mat (Fa)Music mat (Sol)Music mat (La)Music mat (Ti)Music mat (High do)Star PieceNuggetSilver Bottle CapGold Bottle CapMetal PowderClear AmuletRainbow FeatherSilver FeatherRed crystal fragmentDigital cameraStar closetStarry-sky bedStar-shaped DresserStar wall decorationJirachi lampMarine chestMarine closetOrnate decorative shelfSparkling jewelryDangling streetlightCursola lightDecorative clothPrism scale

5 Exercise

5+ items

Punching gameWobbuffet WobblerPunching bagBikeBeach volleyball set

Flavour: bitter

11 foods

Rawst BerryPotatoSeaweedSeaweed saladSeaweed soupRecycled breadBitter hamburger steakSea grapesPopping saladPopping soupCoffee parfait smoothie

Two caveats. The game lists these five in a fixed order, but no source says the first counts for more than the fifth — the numbers are the in-game order, not a strength ranking. And the item lists are incomplete: Serebii marks them as still being filled in, so each count is a floor, not a total.