After seeing so many Avengers teams, I wanted to try a team based on a something, so Adventure Time it is.
Fionna @ Choice Band
Ability: Huge Power
EVs: 252 HP, 252 Atk, 4 Def
Self-explanatory Azumarill set. Nothing else to say, really.
Cake @ Leftovers
EVs: 252 HP, 252 Def, 32 Speed
Team support; Will-O-Wisp for attack drop, Aura Sphere and Psychic so Cake isn't a total set up Pokemon. I considered Espeon for this, but it's probably a bit too frail, even with Magic Bounce...
BMO @ Eviolite
Ability: Trace/ Download
EVs: 252 HP, 252 Sp. Atk, 4 Def
Trick Room set? I've never tried this one before (I've always used a slow Analytic set), but BMO will have enough bulk with evo to set up Trick Room.
Marshall Lee @ Choice Scarf
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Sweep sweep sweep.
Tree Trunks with moustache and tusks @ Leftovers
EVs: 252 Atk, 252 Def, 4 Speed
Rapid Spin support and physical wall. Earthquake for STAB, Ice Shard for Dragon types, and Stealth Rock is self-explanatory. If this was an LC team Phanpy would look more like Tree Trunks...
Ice Genderless-monarch @ Leftovers
EVs: 200 Sp. Atk, 252 Speed, 56 HP
Kyurem w/o DNA splicing; it's a Pokemon worth using on its own. Substitute/ Roost to make use of Pressure, and Dragon Pulse and Ice Beam STABS.
I've thought of others as well, and I'm considering them due to type advantages etc. I also think this might be better as a UU team...
Prince Gumball @ Leftovers
EVs: 252 HP, 252 Def, 4 Sp. Def
Mixed wall; para burn moves, flamethrower over ice beam to deal with grass and bug types.
Princess Bubblegum @ Eviolite
Ability: Natural Cure
EVs: 252 Def, 252 HP, 4 Sp. Def
Chansey will provide much needed team support, but won't be a gender swapped version of a regular character. :I She'll also be UU; if this ends up OU then I'll replace with Blissey so she can hold Leftovers.
Flame Prince @ Choice Scarf
Ability: Flash Fire
EVs: 252 Speed, 252 Sp. Atk, 4 HP
Another sweeper idea? Chandelure can ruin a Blissey/ any cleric or stall set with Trick.
Lumpy (Creepy) Space Prince @ Eviolite
EVs: 252 HP, 128 Def, 128 Sp. Def
Another wall option?
As you can see, I need some help to deal with the synergy of this team. I'll replace Mew with Raikou if this ends up UU.