What do you do when your sister is obsessed with dora and wont let u watch what u want?

We have the same problem with my 2 year old and superman/spiderman. That is all he wants to watch and now that he knows how to say please and thank you it is hard to say no. It is just a phase and soon he will move on to something else.. like batman. I would take the advice of the person who said just get another TV! Keep the peace!