Never done it before but you could try bending some wire (coathanger
etc) or flexible canes (more difficult) into a cat shape then winding
greenery around it and securing with florist's tape then decorating
with flowers/ribbons/bells/toy mice etc. If you didn't want a
plant-type wreaths I've seen ones done with wrapped lollies tied
thickly onto a frame. You could also use short pieces of ribbon,
tinsel, holly sprigs, dried flowers etc. Also just occurred to me that
you could cut the shape out of thick cardboard or similar and fix
decorations to it with glue or twist-ties etc. If the cardboard frame
didn't have a hole in the middle or if the wire wreath was very thickly
decorated you could use wire or pipe-cleaners to add whiskers. That's
all I can think of now... Oh, hang on, what about bread dough? Can be
moulded into any shape then baked and painted or decorated and will
last for quite a long time.

Let us know what you come up with and post some pics if you can.

Kate

The sell them at almost an art and craft store  a Michaels would have them
they would be in the macramé section