Masturbation is a normal part of the human experience and if you like penetration when you masturbate, there's nothing wrong with that either. I'm not sure that a frozen banana is such a good idea, though, because you should avoid putting anything in your vagina that might break off or get lost inside, which a frozen banana might do as it melts.

Also, according to physician, Dr. Karen Rosewater, inserting fruit or other sweet things into the vagina may also encourage the overgrowth of yeast (more for the critters to feed on) and lead to a yeast infection.

It's probably safer to use something specifically designed for this purpose, if you are old enough to buy it. Just make sure it's clean, and that it has a flared base or handle, so that it can't get lost inside.