Whats peoples favourite substance for filling there pants with.

Chocolate pudding!

Rice pudding feels the best

raw eggs

Any kind of Cream Pie in my Rubber and PVC bloomers!
And Chocolate Pudding!

Porridge or oatmeal

Beans in my swimming trunks

Laughter and mud

Wall paint !

Probably very thick natrasol as happened a few weeks ago.

Although there was a time in Scarborough were it went to the vote and I 'won' (or lost, depends on your perspective) a game called 'Custard Shorts' and getting it filled with the classic yellow stuff was pretty amazing. I wonder if anyone who was there remembers this???

Chocolate, doubly so if I'm wearing white panties. And I often am since it's my second or tied for my second favorite color to wear behind pink.

Golden syrup.

In particular, when wearing a leotard or women's one-piece swimsuit as underwear. Pour the syrup in and then enjoy the feelings as it flows down and gathers in sensitive places, and the knowlege that it will, slowly, seep through the underwear and eventually also mess up the clothes you're wearing on top, but it will take a lot of time, and wonderful squelchy feelings, to do so.