When a minifigure is new, the joints where its legs joins its hips is relatively stiff. However, when a minifig gets old and has been used a lot, this joint can get very loose leaving its legs very floppy. Why does this happen? Is there a risk-free way to re-tighten this joint?
I would try pulling off the legs and dropping a tiny, tiny amount of plastic glue on the hinge, smooth it out and let it dry, then put the leg back on. It should provide enough friction to the leg again so they aren't so loose.
This video has a pretty good method: https://www.youtube.com/watch?v=rEkVPVgonRk
If you don't want to watch:
- Pop both legs off the hips.
- Rip off a small square of paper, preferably tissue paper.
- Place it over the hole in one of the legs.
- With the paper still around it, forcibly snap the leg back into place.
- Repeat for the other leg.
- Rip off any excess paper that is around the minifig.
- If the legs get loose again, repeat steps one through six.