Something to keep in mind, just because Masskid may be claiming sunglasses with Squirtle doesn't necessarily mean he is a doctor / protector. If you don't know the sunglasses squirtle's history that well, here you go :
Ignoring the fact he did join Ash at the end, I'd just like to point out Squirtle was his own little gang/mafia.
So personally - I'd wanna vote Masskid next on this but I'm not rushing it due to the fact he's on the road at the moment. I'd like to hear from him when he gets back home, even if it's going to be the random bickering.