Model it out of fondant as the topper. Or you could do the monkey face as the cake.
btw - this is the cutest darn monkey i have ever seen
just take it one part at a time, and this is a good one to start from, think of them all as rounds and then mold from there - the face looks like 2 rounds and then shape them into the monkey - then do the body as a round and then the arms as snakes and the legs as snakes with the feet as rounds etc....
i hope that makes sense - and keep the monkey on the table so you have something to refer to.
HAVE FUN!!!
I think a white cake with pink hearts and the monkey as the topper with a number (age) out of fondant too (snake shaped to number). HOW CUTE!!!!!!!!
Here is a link to a video on You Tube by Aine2. It just shows how to do a monkey face, not exactly like yours but maybe it will help to see it done.
Anyway... hope that helps a little.
If you want to keep the figure, may I recommend you use 50/50 fondant/gumpaste, or at the very least put gumtex in your fondant. It will make your life easier when trying to model the figure as it will dry faster with minimal sagging, and will get rock-hard for long-term storage if you use 50/50 (see that Remy in my avatar? I still have him, a year later). Store away from the direct and indirect sun; the red colors (both in its cute little pink toes, and in the brown) will fade in the light.
Fondant modeling is easier than you might think, esp. if you follow the PP's advice. I did it for my second cake ever, it was a bunch of little zoo animals (including a monkey, but he didn't look like yours) and the advice about starting with round shapes is solid, that's exactly what I did and they were easy and fun.
Good luck and have fun!
Here's a cake I did that's similar to your toy. There is a pic of it in my photos, but this link also gives you in-progress pictures of it that might help you make it if you wanted to go that route:
http://www.cakedalaska.com/Caked_Alaska/Monkey_see.html
HTH,
Deanna
I love the idea of the pink and white w/ ribbon. You could do 2 layers, the bottom layer pink with brown and white stripes and pink ribbon around the bottom. The top layer could be white with hearts on it like the ones that are on the bottom of it's feet and the same pink ribbon around the bottom of this layer. Then the fondant/gumpaste monkey on top! Ooooohhhh!! This monkey is so cute! I can't wait to see what you do with it!! 
Good luck!! 
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