I have made a couple fondant babies, but a few days ago I made my first fondant "Boy". He was in a sitting position. He is for a cake due tommorrow. I did not notice at first, but over the past few days his head weight has caused his body to sink more and more. Now he looks like he has a HUGE belly. Any tips on how to prevent this if I make him a new body?

You could let him dry before you put on his head. Aine2 has some great tutorials on making figures and she uses a stick of spaghetti to attach the heads but I think she lets the bodies dry first.
You could also use a polystyrenne ball covered in fondant for the head which would make it a lot lighter.

can i see a picture of your fat boy?

Mixing fondant with tylose will help it dry faster and be less likely to sag.

I make figures all the time. I mix RF with some GP and do them in steps. I let the bodies dry for several days before I continue.

I second (or third?) the suggestions to either add powder (gumtex in my case) or make em out of 50/50 fondant/gumpaste. If you look closely at the panda in my avatar, he also developed a sagging belly (although he was actually made out of mmf and the others were out of wilton...but he was my "lesson learned" and I started using gumtex or 50/50 after that).

I definitely put heads on after the bodies dry, though you may be able to skip that if you are using 50/50, or of course if your figure is quite small. I do the spaghetti thing too, super helpful to keep parts in place while the connecting "glue" dries, and helps keeps parts from sagging into supporting parts while everything firms up.

oh come on now, show us your pot bellied little guy.

mommachris

I like adding gum-tex because you still get to play around with the figure longer than when gum paste gets added into the mix. But, the gumpaste will make it dry harder.

S.