Subsurface scattering is a property of materials where light hits a semitranslucent material, bounces around inside it interacting with the material, and exits at another point, usually in a different color. This can mean a material retains light bouncing around inside it even when very little light is present. For example, subsurface scattering is why human hands look red and translucent when a light shines behind them, and why a gelatinous substance like gelatin or even fruit like a grape appear to be evenly illuminated even when light strikes only their edge. I recently hypothesized Pikmin 2 appears to try and emulate this property using simple methods for various materials. So far, I've seen this with nectar or spray droplets, white bramble gates, and the fronds of Candypop Buds. Keep in mind the lighting engine in Pikmin 2 does not actually accurately calculate this effect; instead, it seems these objects are merely less sensitive to fog.
Pikmin 3 does this with most of its fruits and the Onion legs, with a more realistic shader to get the effects more accurately. I'm sure there are many instances of subsurface scattering in Pikmin 3, but I don't have any photos to demonstrate quite yet.