How would i replicate this look? I want to make some of the pokemon characters and have tried putting a transparent shader, a glass shader, and translucent. I have tried in both blender internal and cycles. I want it to look quite cartoony, but have no idea how to achieve this look.
I suggest using Irie's OSL toon shader in Cycles (read this), in combination with a Layer Weight or Fresnel node on the bubble's toon shader to phase between the light and dark green. You could even use that Fresnel technique to control the transparency of the bubbles, which may look even better. If you want it to look more or less exactly like the reference art, you may want to composite the internal character (X-ray style) to always show in front of the bubble's material - but the bubble's outline should always be in front of the character.
You'll have to adjust the settings to suit your model and lighting. I used a couple of lamps, only one that cast shadows. Increasing the 'Fac' of the mix shader on the inner object material makes it brighter, and the two in the slime material control the slime's brightness and transparency. (Left is transparency, right is brightness.)
I used lamps with a size of zero to make the shadows sharper.