It appears that Marfet says different things to different players, possibly depending on the quests that they have completed and/or the Kudos they have earned. It is also possible that Marfet's chat has been changed.
When you talk to Marfet, he may say that he knows who Bob the Jagex Cat really is.
When a player speaks to Marfet, at least some of the time, the player asks Marfet if he has seen the Digsite Exhibit. Marfet responds that it is good and asks if you have done the quest. He then informs the player that they can get the teddy bear back by stealing it from the female student.