Bobble head dolls are a fun, campy craft item. At its basic level, a bobble head doll is nothing more than a freestanding figurine with an oversized head (or, sometimes, whole upper body) attached to the body via a small spring. These are very simple to make, so there are a variety of ways to make them.
The first piece to consider is the main body of the figurine. You can make the body out of any objects that resemble the person or character, including dolls or action figures with the original head removed. However, the body must be rigid, capable of standing on its own, and have enough weight to it that tapping the doll's bobble head will not cause it to tip over. An extremely basic way of doing this is by using an empty single-serving yogurt or similar plastic container filled with rice and glue for weight, then covering the container with construction paper or craft felt "clothing." Whether you build your own doll body or use a pre-existing doll, make sure it has a flat, solid surface for the spring "neck" to attach to.
When you make the head of the bobble head doll, remember that it should be oversized for the body. Bobble heads are usually reminiscent of caricatures, using giant heads with exaggerated features to make a person or character recognizable. While sculpting or molding a three-dimensional head is an option, it is difficult and can be expensive. Alternatively, you can make a head out of a plastic foam ball with a photo of the person's face and a shallow hole underneath for the spring. You can even make a head out of two equal-size circles of paper with photos or drawings of the front and back of the person's head, connected back-to-back on all sides but the bottom and then opened to slip over the spring.
The spring is the simplest part of a bobble head to make. Almost all bobble heads use the same type of spring, and since it is concealed, it doesn't matter much what it looks like. Some thin craft wire, wrapped around a standard ballpoint pen, makes a perfectly workable spring for your bobble head. Remember, though, to bend the ends of the spring inward to form a complete, closed circle at each end; otherwise, the head may sit on the doll at an angle. How you attach the spring to the head and body depends upon the materials you use for them. If it won't damage the materials you are using, hot glue is generally a good choice; otherwise, standard white glue will work.