Is it sinful to base your life on a cartoon? Let's say you're being tempted, but to help you get past your temptation you think about what a hero on a show would do. Would that be sinful?
A lot would depend on the cartoon I would think. Behind every cartoon is a set of people creating the cartoon. Cartoons present a simplified version of the world, but they will naturally follow the thoughts and biases of the people creating the cartoon.
The apostle Paul told people, "Imitate me, just as I also imitate Christ" (I Corinthians 11:1). Notice that Paul didn't just say, "follow my lead." He told people to check first that he was following Christ and then follow him as he followed Christ. Similarly, Paul told Timothy, "And the things that you have heard from me among many witnesses, commit these to faithful men who will be able to teach others also" (II Timothy 2:2). One person passes down what they learn to the next. But again notice that it isn't just any men, but faithful men.
People learn in different ways. Some are able to pick up an instruction manual and gain all sorts of knowledge. Others need to hear the instructions read to them in order for it to stick with them. Still others rather see it done and then it makes an impression on them.
God provided different means for people to learn His will. The Bible is in written form so anyone can pick it up and learn from it. But God also sent out teachers to talk about the message. "How then shall they call on Him in whom they have not believed? And how shall they believe in Him of whom they have not heard? And how shall they hear without a preacher? And how shall they preach unless they are sent? As it is written: "How beautiful are the feet of those who preach the gospel of peace, who bring glad tidings of good things!"" (Romans 10:14-15). And God asks his people to leave examples for others to imitate. "Let no one despise your youth, but be an example to the believers in word, in conduct, in love, in spirit, in faith, in purity" (I Timothy 4:12).
So, if your cartoon character is giving a good, godly example and thinking about it helps clarify in your mind what you ought to do, then there is nothing wrong. However, you remain on guard. You can't assume that the cartoon character is always right. You still need to match what is being shown against what the Bible teaches. And sometimes what is wrong can be very subtle. "Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world" (I John 4:1).