Our Maya does that too !!
She is 6 months now !! When she sits on the bed while we still lay under the covers , she searches around untill she finds my feet and then she bites , right through the covers !!! Ouch ...!!!

I surely hope she will outgrow this , cause it hurts ... !!

My prevous cat Sydney (at RB !!) did not do that ; he jumped on my feet as he discovered them or if I was teasing him by moving my toes !!