You can change what he says like so:

Merlin.speak("Hello, i am brandys wizard and i have been sent here to tell you about the van");

That is the command for him to speak. You can change any of the text between the "" marks

A list of other commands:
Animation.AddItem ("Acknowledge")
Animation.AddItem ("Announce")
Animation.AddItem ("Blink")
Animation.AddItem ("Congratulate")
Animation.AddItem ("DoMagic1")
Animation.AddItem ("DoMagic2")
Animation.AddItem ("Explain")
Animation.AddItem ("GestureDown")
Animation.AddItem ("GestureLeft")
Animation.AddItem ("GestureRight")
Animation.AddItem ("GetAttention")
Animation.AddItem ("LookUpBlink")
Animation.AddItem ("MoveDown")
Animation.AddItem ("MoveLeft")
Animation.AddItem ("MoveRight")
Animation.AddItem ("MoveUp")
Animation.AddItem ("Pleased")
Animation.AddItem ("Process")
Animation.AddItem ("Read")
Animation.AddItem ("Sad")
Animation.AddItem ("Search")
Animation.AddItem ("Show")
Animation.AddItem ("Think")
Animation.AddItem ("Wave")
Animation.AddItem ("Write")

There are also three other characters.

Peedy the parrot (accessed as peedy)
Genie (accessed as genie)
Robby the robot (accessed as robby)

Steve