The answer to your question would be that the sentence that expresses the same idea in a complex sentence is the following one: I cannot way to see this movie because the main character is played by my favorite actress.
A complex sentence has one independent clause (a) and at least one dependent clause (b). The difference between them is that independent clauses can stand alone as a sentence because they represent a complete thought (a).
a) I cannot way to see this movie
b) * Because the main character is played by my favorite actress