"my job is to make my professor happy"

I had a wonderful discussion today with a friend of mine. He is TA (teaching assistant) for some professor in the school. TAs are responsible for administering tests, check tests, take attendance and etc. So basically they are responsible for the less interesting part of the teaching process.
So we've been talking about situation that he had with one of his students and he said at some point that his job is to make his professor happy.
Well isn't that a very hard job to make someone happy? People are so unpredictable. On the other side - isn't it the easiest job ever? All you need is to make your boss to smile and treat t as his happiness.
The funny thing about it was that it can be translated to my language also as satisfied. And we often use this expression "my only responsibility is to satisfy my boss" referring to our jobs. But this expression has 2 meanings one of which includes sexual context. People use this expression as a joke all the time. If only my friend knew what I had in my mind when he said about making his professor happy... I'm sure he would not say something like this again... :)