Macbook Pro Retina Heat issues

I just got a new Macbook Pro Retina laptop last week ( 13.3"/2.7GHz/8GB memory/128 GB storage) but brought it back to the apple store since I noticed that it would get really hot. They replaced that one and gave me a new one yesterday. The same problem is happening again on this one though. It gets really hot when I watch a movie, about 30 mins in. The bottom of the laptop is really hot, as well as around the keyboard, and the left/right corners. I've tried to keep it on a glass table since that allows for plenty of air circulation underneath, but it still gets hot, although its not as hot as earlier. I have done a basic diagnostic test (took 2-3 minutes) but the results said that "no issues were found".Could anyone explain why this is happening and what I should do to fix it?Should I return this laptop?