Just curious, has anyone ever thought of pairing up this Donkey Kong rip off with a Kecleon in doubles? Kecleon does get Skill Swap as an Egg Move, and while he has a base 40 Speed, he does get Protean as a hidden ability...
Slaking- King Kong
- Ability: Truant
- Item: Expert Belt/Life Orb
- Nature: Jolly (+ Spd, - Sp. Atk)
- EVs: 252 Atk/252 Spd, 4 HP
- Giga Impact/Return
- Earthquake/Rock Slide
- Shadow Claw
- Fire Punch/Thunder Punch/Brick Break/Slack Off
With any Protean Pokemon in general, you can basically do whatever you want. This set works similar to every Greninja set out there: switch in and destroy with unlimited STABs. Getting off a Skill Swap with Kecleon is the difficult part, but if you can manage to find a way to do it without it dying first, Slaking will gain the ability to hit stuff... hard.
Return is a heavy hitting move, no matter how you look at it. It will get STAB without Protean. Giga Impact is an option just in case of not getting Protean quick enough. Earthquake is your most powerful move. It will hit anything and everything that isn't flying. Rock Slide is also another option, depending on what you want for your team. Shadow Claw takes care of ghosts. The last slot is whatever else fits. Fire and Thunder Punch both take care of Skarmory and Ferrothorn, a couple of things that can survive an Earthquake with ease. Brick break is for any other Steels or Normals that feel like opposing you. Slack off heals damage from Life Orb and any other damage Slaking takes. The only reason Hammer Arm isn't on here is that is comes with a speed drop, which a sweeper does not like.
I've only taken a quick look at King's moves. I haven't really dove into specific movesets. However, whichever moves you choose, a Protean Slaking is something to be feared.
Another plus: you can use Kecleon to give Protean to other Pokemon, if it survives.