Time for some blink! With 5X 3mm LEDs.
Put a little dob of hot-glue in the hole.
Quickly press the LED in before the glue cools.
Bend the negative leads over each other until you get to the end - clipping the excess as you go.
I stripped the insulation off hook-up wire to cover the leads. Shrink tube can also be used, you'll just have to make sure that you don't get the area too hot - it might re-melt the hot-glue.
Organize the leads so that LED one and five, and two and three are connected.
Trim three 330ohm resistors.
Solder them all in place.
At this point I did add some clear shrink tube to help with strain relief. You could also coat the area in hot-glue as well.
Just a touch of hot-glue to stick the two pieces of the mouth together.