Pedagogical Agents are animated lifelike software agents that operate in digital learning environments to interact with and support learners in a conversational style, mimicking the responsive one to one interaction that a learner may get from a human teacher edutechwiki.unige.ch 
Pedagogical agents can appear on the screen (like the Microsoft Paper Clip) or Teacherbots) or they can be a personalsed robot toy (driven by an Android phone) like the Dragonbot.
YOUTUBE J2n0IqH76-Q Dragonbot MIT Media Lab
Teacherbots are screenbased bots that use platforms such as Twitter to interact with students.