Line a baking sheet with wax paper.
Peel the bananas and then slice them in half width-wise. Carefully insert a stick into the bottom of each banana and then place it on the baking sheet. Freeze the bananas for 1 hour.
Melt the chocolate chips with the vegetable oil in a deep metal bowl set over a saucepan of barely simmering water, stirring occasionally, until the mixture is smooth. Remove the bowl of chocolate and set it aside.
Remove the bananas from the freezer, and one at a time, dip them in the chocolate, smoothing it over the entirety of the banana with a spoon. Immediately sprinkle the banana with the assorted sprinkles and then lay the banana on the wax paper-lined baking sheet. Repeat the dipping and decorating process with the remaining bananas and then return them to the freezer for 10 minutes, or until the chocolate is firm.