Because most characters are going to be shown in timebased mediums (web, TV...) they are usually designed with at least few different frames so a dynamic style is also defined (how the character should move), and creating a simple movement can be easily solved.

That simple animation that defines the character without meaning an action or story being told is called the Iddle stage of a character. You might be familar with this from gaming. Idling allows to better define a character in his world and reminds the interactive user to make a move and activate the screen's capabilities.

Below you have another animated example of a character in his world.

This animation was created for Carbon 14 Creative agency. The agency's logo was a hippo, as you see on the card.

As you play with the flash "postcard" remember to activate elements, the sun and the anchor to see the Charcater's world in action.