The Alien Brain Visitor is simply a brain with three large purple tentacles that he uses for movement and holding things, and two large, bulging eyes attached to pink stalks. During the first few minutes of his appearance, he hides himself in a dark green trench coat far too big for him as well as a black hat with a brown band.
The Alien Brain Visitor obedient and determined, diligently following the Alien Brain Boss' orders and using simple deception to get what he needs. Near the end of the episode, kindness in liquid form is thrown into his eyes and he becomes friendly and polite. He doesn't appear to know Earth's languages or technology very well, speaking in short, broken phrases usually ending in "yes," shaking his head in a "no" motion whenever he says "yes," and picking up a rotary phone by its base and speaking into it without dialing.
The Alien Brain Visitor lands his ship outside the Bagge Farm and comes to the door in a disguise, claiming his car broke down and he needs to use the phone ("Car Broke. Phone, Yes?"). After being welcomed inside, he incorrectly uses the phone and sits himself in Muriel's rocking chair while Courage eyes him suspiciously. He begins to check off various emotions on a clipboard and notices he is missing kindness. He quickly disposes of Courage by locking him in the closet and begins to use his tentacles to search for emotions in people's heads. He comes up dry with Eustace, but finds an ample supply of kindness in Muriel, which he inserts into a large test tube. The newly unkind Muriel promptly kicks him out of the house and he returns to his ship, where he presents the Alien Brain Boss with kindness. He attempts to start the ship, but Courage removes the battery and climbs inside the ship to reclaim Muriel's kindness. He battles briefly with Courage and ends up having kindness thrown in his eyes, which turns him into a courteous gentlemen. He lets Courage exit the ship and warmly accepts a parting gift from the dog, a lit bomb. It explodes, presumably killing him, but the ending reveals countless others like him at the Bagge Farm.