Emitter

From LittleBigPlanet Wiki

An emitter is an object which makes you get your level more fluid and with more movment. Levels wthout emitters areen't very good because nothing appears or disappears so theres really no action. You can only emit items that:

• You got on Story mode.
• Explosives and bubble prizes,points.
• Items you saved on "My objects".
• Items of community.

To use good an emitter is preferably to use a switch.