CAN SOMEONE PLEASE HELP? -REWARD-?

Hello, I'm Jay. I have a youtube channel and I want to make animations like Splashkittyartist :] But I can't find an animation program that works. It has to be free (My mom won't buy the toonboom one or anything) and I have firefox, so it has to be able to run with that. If anyone knows any animation program that is good PLEASE tell me. If I like the program and use it I will make you a character and it will be in TWO of my videos. If two or more people say the same thing I might make a characters for each of you. Please PLEASE help. Thank yooh. (And no mean comments please)