Are those NURBS? I don't think you can do that. No, I'm quite sure that you can't do that. Well, that's unless you do alot of cutting and rebuilding in those surfaces (for example, you can cut each leg on the inside to alow it to open and then you fill the new empty space with 2 new surfaces) But I don't think that's a good idea anyway.

If you are going to be dressing him up then don't bother filling that space (or just put a sphere in there to help the cloth calculations), but you don't need to conect anything.

But if you still want to close that some how then you will have to start over (at least with the legs). I'm feeling to lazy to type up instructions right now so do find out all what you can about patch modeling and that should help you close that area. And then if you have any problem or more specific questions I'll probably be awake by then and able to help you more.