How will you know if a child don't like you?

I'm confuse by my 6 year old cousins they said to me that they hate me because I'm fat, but at the same time they are laughing and giggling while they said those words and at the same time also invited me to their seemingly tea party and game of house. What's really going on?
It's not the first time I met them and not the second as well, but all those visits everything turns all good even though they kind of played those little pranks on me like hiding my shoe or designing my bag with crayons or placing their stuff inside my bag to make it heavy as they would ask me if it's heavy.
Oh yeah they also throw their dirty panties on my face and they would be laughing.

They always play pranks on me, but it seems to me they respected me as well. Like for example, one time I was bringing home some groceries for my aunts and uncles and it fell and they immediately rushed in to help. When they want to borrow my iPhone and when I would say later, not now or no they would not bother me about it again until the next hour or so (Yes! I let them use my phone for games, but there are times I need my phone ). Oh yeah when they are using my phone and I got a call they would rush to me and tell me that my phone is ringing same also with text messages.

Do they play pranks on me because they don't like me? The pranks are not bothersome at all to me, but just makes me wonder what is the motive behind it.

They're still young and such bullies. It's the age where they're learning to argue back. Yet, their mind is still young. It doesn't mean they dislike you. They're still young and learning. If they're really really rude, I suggest you let their parents know.

Tell them how you feel or tell the parents how you feel

They are not bad kids they just don't have boundaries. You need to be assertive with them. If you don't like being called fat tell them not to be mean bullies.

No. They like you. There just a couple of dumb kids. The, "Your Fat." comments aren't very nice though. You should tell them that it's not nice to make fun of people cause of the way they look and that it hurts your feelings…" 'would you like it if I called you ugly?' No. So don't be mean to me like that." I'm sure some of their pranks on you get a little out of hand… Tell them that you don't mind a few innocent pranks here and there but tell them they need to be respectful to a point and not get carried away and do anything dangerous. These kids see other kids doing these stupid pranks on people on youtube and think it's funny. Let them know that, yah. It is, but to a certain extent. I've always talked to kids like they are adults and I've got a lot of respect that way.