Well, what sets this sea slug apart is its ability to store chloroplast from the algae it eats and use it to make its OWN food!
The immature sea slug is brown in color and the color changes as it matures and accumulates the chloroplast.
As the slug eats the algae it "sucks" the contents of the cells out and does not fully digest it, but rather stores the chloroplast within its digestive cells and other body cells. These "kidnapped" organelles can survive between 9 months and a year and function just as if they were in the algae, producing glucose via photosynthesis. When deprived of food these sea slugs are able to get all of the energy they need from the chloroplast they contain.
Can WE do this?
Short answer is NO, for many reasons but one that sticks out the most is the fact that chloroplasts can not function on their own. As you know chloroplast contain their own DNA, but they only contain the instructions to make 10% of necessary proteins used in photosynthesis. This means the sea slug makes the other 90% of the proteins necessary, something nearly no other animals can do.
Also, being a small aquatic creature, they use very little energy, the chloroplast needed to fuel our 2,000 calorie life style would take up an area nearly the size of a football field.