This pattern has been copied from the Age UK website it was one of the first novelty hats that I tried knitting, and still a great design.

Instructions:
Using 4 mm needles, cast on 32 stitches in yellow double knit
Knit 2 rows
Beginning with a Knit row, continue in SS throughout:
Row 1: Knit
Row 2: (P3tog, P1 K1 P1 into the same stitch) repeat to end
Row 3: Knit
Row 4 (P1 K1 P1 into the same stitch, P3tog) repeat to end
Row 5: Knit
Repeat rows 2 to 5, twice more.
Row 14: (P3tog, P1) repeat to end
Row 15: (K2tog) repeat to end
Row 16: (P2tog) repeat to end
B & T tightly

Large Leaves – make 2
Using 4 mm needles and green, cast on 5 stitches
Row 1: K3, YO, K1, YO, K1 (7 st)
Row 2: Purl
Row 3: K5, YO, K1, YO, K1 (9 st)
Row 4: Cast off 4 stitches and knit to end (5 st)
Repeat Rows 1 to 4 once more and then rows 1 to 3 again
Next row: Cast off all stitches

Small Leaves – make 2
Using 4 mm needles and green, cast on 3 stitches
Row 1: K1, YO, K1, YO, K1 (5 st)
Row 2: Purl
Row 3: K3, YO, K1, YO, K1 (7 st)
Row 4: Cast off 4 stitches and knit to end (3 st)
Repeat Rows 1 to 4 once more and then rows 1 to 3 again
Next row: Cast off all stitches

Making Up:
Roll up the large leaves and sew the base of the leaves together. 
Sew the small leaves around the base of the large leaves and then all of them onto the top of the pineapple.