Once the cake is cooled, use your hands or two forks and to crumble the cake into fine crumbs.
Add 1 tablespoon of sprinkles and mix it into cake crumbs. Repeat this until the sprinkles are distributed evenly among the crumbs.
In a separate bowl mix the cake crumbs and the buttercream. For every 1 cup of cake crumbs add 1-2 tbs of buttercream. Mix with hands or fork until the buttercream is fully incorporated. You want the mixture to be just moist enough to roll into balls.
Using a small ice cream scoop, scoop out a small amount of mixture and roll between cupped hands until you reach the desired round shape.
Put balls on a plate and cover with plastic wrap. Place in refrigerator for at least 4 hours.
Place coating chocolates in a deep bowl so you will be able to submerge the entire ball in the chocolate. Melt chocolates.
Dip lollipop stick into chocolate and then into the middle of a cake ball.
Dip cake ball into the chocolate until it is completely covered. Hold it sideways over the bowl and rotate it and tap it so the excess chocolate comes off.
When the excess chocolate has dripped off, push the lollipop stick into styrofoam block to dry.
Once chocolate is dry, paint the top part of the ball around the stick with piping gel and add sprinkle decorations.
Place each pop into an individual mini cupcake liner.