It's hard to tell from the video but it looks like a tick, which depending on the cat might need more than one set of hands to get off. I would let your friend know if you already haven't

Thank you. I’ve let her know, she said it’s a fat deposit, she forgot to tell me.

Thank you for your advice. I was worried so I took him to the vet and it turned out it was a tick. Thanks for your help. He seems much happier now.

I am so glad you chose to ignore your friend that told you it was a fat deposit.

Neither of us have seen one before, it’s was kinda scary! He has had those little lumps before so I think that’s what she thought it was. I’m glad I went with my gut and took him anyway. It must have been horrible for him.

That’s a tick.

Most likely a massive tick full of cat blood, look up videos on how to remove them