What does this mean in Cat?

Kittens are 10 wks old.

Our Foxy sometimes act pretty crazy. She would arc her back, ear flatted, looks like scared but running around in the room instead of hiding. Sometimes she did that while jump to her brother and start "fight". Normally she likes to be with human and purrs when pet her, but at these times she would try to escape away quickly and avoid touching from us.

What does all these mean? Does she really feel scared or she's pretending something? Thanks!

Well I did some search and probably found the answer, Foxy is just make up some situation and practicing the activities she might use when grow older.

Interesting thing is that Soy never act like that... When Foxy got her favorite toy, she would growl with toy in mouth, or even hiss when Soy is too close... And if Soy gets that, he would want Foxy's attention, sort of "intentionally play near her"

I'm glad you found your answer!

Your kittens are adorable!

She is prey fighting, it is a defensive manuever that kittens learn as they grow, preparing them for adulthood, either to help them hunt or to prepare them when they do fight. Getting her spayed will greatly decrease this type of behavior.