Peanut can sit from laying

Little peanut has been sitting for quite awhile now... (I put the boppy behind him most times so that if he falls backwards, he doesn't bang his little peanut head)  well, now when he is completely laying on the boppy he can get back up to sitting easily.  He had done that several weeks ago but now he can do it very easily.  Now he kinda gets a kick out of it... he is rolling all over the house.