Step one:
First draw an oval, making sure the bottom is sharper.
Step 2:
Then draw several shapes of different sizes.
Step 3:
Then use small polylines under each oval to draw its lower part.
Step 4:
Connect them with a few lines.
Step 5:
You can also draw a bow on the connected parts.
Step Six:
Finally, apply nice colors and the colorful balloons are ready.