Peel the banana then cut it in half. Slice each half length ways so you have 4 equal pieces.
Carefully insert a lolly ice stick into the cut end so it holds the banana securely.
Dip each banana into the yogurt then place them on a piece of baking parchment.
Put them in the freezer until the yogurt is frozen (this shouldn't take too long).
Melt the chocolate chips in the microwave in short 10 second bursts, checking after each 10 seconds. When they start to melt, stir until they are smooth.
Make a small piping bag using a piece of greaseproof - fold a square of greaseproof into a triangle then into a cone shape then fill with the melted chocolate. Fold over the top and snip a tiny hole at the end.
Pipe 2 eyes and a mouth on each frozen banana then pop them back in the freezer until you're ready to eat them.