A small quantity of DK yarn
A contrast colour for the pompom tail.
A blunt-ended sewing needle.
Use running stitch to sew a triangle shape on the knitted square, as in the picture. Obviously it's better to use matching yarn for the sewing.
This bit is a little fiddly and I had to experiment a little to get it right. Make sure the yarn is secured very well at the top.
Firmly attach tail to bunny.
It's cute though.