Can I use a TV character in videos?

You can not use a TV character in your videos without the permission of the television program owner.

Bad idea. The short answer is no, as not only copyright law may apply, but also publicity and personality rights. While the law allows for certain parody uses of characters under the federal fair use provisions of the Copyright Act, there are other factors in play here. Note: it does not matter that much if you make money off your derivative work or not - you still need to obtain (preferably, written) permission to use others' work for secondary purposes under copyright law. Of course, if you are not using content for commercial purposes, there is less likelihood that anyone will seek to recover damages from you, but it is still probably not worth the risk here.

Talk with a creative knowledgeable lawyer about what your plans and goals are. Do you remember the "Real Live Brady Bunch"? These were stage shows and later a movie, that used the exact scripts and characters from The Brady Bunch. There are ways to do such things, but you need a good lawyer. It is often possible to get licensing for what you want to do.