5 is an evil number.

If you remember well on 1B, You can see Woody being scared of the number five.

Also, What number of petals does Flower have? 5. (Though she started being nicer in newer seasons, but that doesn't change the fact that she can be sometimes mean in newer episodes)

Also, Pentagons have 5 sides (or however you call them), and Pentagons are evil as seen on 4S 1Ep.

That's my dumb theory for now, so bye.