Suitable for beginners. Crocheted easily and quickly. 
Children will like it! The badge can be worn on a backpack or piece clothing.
Materials:
Yarn of your choice (acrylic or cotton). I used cotton yarn, 425 m/100 g. Size 7 cm x 3.5 cm.
Yarn colors: red, light green, dark green, black.
A crochet hook, I have 1,25 mm crochet hook
For the eyes: 2 half-beads, I used 6mm diam half-beads and white piece of felt
Transparent glue
A sewing needle
A piece of thick cardboard
Brooch base (fastener)

Abbreviations:
sc – single crochet
inc – increase (2 sc in 1 st)
(...) x N times – repeat instructions in brackets N times

Start with red yarn.
1) 8 sc in a Magic Ring
2) (inc)× 8 times (16)

3) (1 sc, inc)× 8 times (24)
4) (1 sc, inc, 1 sc)× 8 times (32)
5) (3 sc, inc)× 8 times (40)
6) (2 sc, inc, 2 sc)× 8 times (48)
7) (5 sc, inc)× 8 times (56)
8) (3 sc, inc, 3 sc)× 8 times (64)
9) 64 sc
10) (7 sc, inc)× 8 times (72)

Fold the part in half, circle it on the cardboard, cut out a semicircle.

Change to light green yarn
11) 72 sc

Change to dark green yarn
12) (11 sc, inc)× 6 times (78)
Do not cut the thread!
Sew a fastener on one half of the circle. Glue the cardboard semicircle on the wrong side.

Take a pair of half – beads or ready - made eyes. Take a piece of white felt and cut out 2 circles to make the whites of the eyes. They should be slightly larger in diam than the beads. Glue the eyes on. Make sure the side of the white felt is showing. Glue the eyes to the other half of the circle.

Embroider a smile. Make some dotted lines and then wrap each stitch around with yarn, (see the pictures).  Thus, the smile will be smooth.

Embroider the eyebrows. Embroider seeds with black yarn. 

Fold the part in two, work 39 sc by hooking through both edges of the part.

Fasten off, cut off.
The watermelon slice badge is completed!