Sure, and very cute idea!
Just make a bunch of tiny teapot shapes from polymer clay (see below), then stick them onto the heads of pins, and bake.
You could put them on short "applique" pins, or on any other size of pin with a small head or with the head cut off (garage-type wire cutters or toenail cutters, etc, suggested).
Or put them on regular-size flat head (silk) pins, or on pins of any kind that have heads trimmed off, or on stiff wire if you don't need a sharp point.
If necessary, make a hole or slit in the raw clay teapot first (I assume the bottom), then put the clay on the pin heads (and gently snug any clay back around the heads), or just press the pin into the clay teapots if no heads.
It may help (especially for the softer brands/lines of polymer clay) to put the teapots in the frig or freezer awhile or let sit out overnight, to make them firmer before making the holes.
You can use a bit of glue when you insert the pins. Or, if you make the hole before baking but insert the pin/wire after baking, a bit of superglue can be good (press in a hold 10 sec).
...But if the clay is snugged around any pins with heads, you won't need glue. Or if you just bend
or zigzag the end of the pin a bit before inserting it into a premade hole or slit, you also won't need glue.
Btw, even plastic heads on some kinds of pins will be fine baked with the clay and especially since they'd be inside the clay which will insulate them too.
As for making mini teapots from polymer clay, those can be made in pretty simple shapes.
Check out some of these miniature teapots (and most could be downsized):http://glassattic.com/polymer/miniatures.htm
(click on the Dishware
category, then scroll all the way down to its Websites
subcategory for various teapots--sorry some
of those links won't work)
For this one, e.g., a ball is the main part, which topped with a squished-ball disk, then tiny ball...another disk for the base... and tapered logs added for handle and spout (if those are too thin or stick out too much, they could break off with too much stress later)...and perhaps a hole in the spout end made with a toothpick ...be sure to join the parts well**http://farm4.static.flickr.com/3211/2449583510_aca4b21ab3.jpg
(teeny teapot on stove)http://www.marcysclaypen.com/teapots/teapots2.htmlhttp://www.marcysclaypen.com/teapots/teapots.htmlhttp://www.polyclay.com/mini.htmhttp://www.pennymichelle.com/teapots.htmlhttps://www.google.com/images?q=polymer+clay+miniature+teapothttps://www.google.com/images?q=polymer+clay+teapothttps://www.google.com/images?q=polymer+clay+teapot+bead
** for joining parts securely, check out this page too:http://glassattic.com/polymer/glues-Diluent.htm
(click on Some Bonding Techniques