My cat started growling, hissing at something on our ceiling fan and then it disappeared

Last night at around 1 am, I was watching TV and then I started to hear noises coming from my ceiling fan in the living room, it sounded like someone was walking on it or something was on top of it and was scratching slowly. Then my cat started growling and hissing at it then the fan started to shake, I swear someone was really on it because it was making a lot of noise, I know the fan was dirty and had a lot of dust on it, but this was a very heavy noise. Then I grabbed my cat, hoping he wouldn't scratch it and run away, and I went to my room to watch the rest, but then the noise just disappeared, complete silence. I swear this was paranormal because no animal can climb on a fan, it wouldn't even hold its weight. I don't know what it was.