Unlike the other people living on Earth, Blockhead is a different-looking humanoid. He is always seen wearing brown shoes, blue jeans and a red long-sleeved shirt. Blockhead has bright yellow skin and a round head, which resembles a smiley face. His tongue is somewhat longer than a normal human being's tongue, which allows him to use it in order to grab stuff far away.

In later episodes (more noticeable in the Ghostmas episodes), he wears a white short-sleeved shirt with "#1" written on it over his longer shirt. This is also relevant to the fact that he calls himself the "#1 guy".

Extremely dimwitted, undereducated and somewhat (though unintentional) destructive (though well-meaning), Blockhead constantly ignores his Conscience (much to the Conscience's irritation) and unintentionally tends to wreak havoc on his surroundings and other people. As a result, he hardly ever has to pay the consequences of his actions. Blockhead also has a number of weird quirks, such as wielding radishes for weapons, celebrating "Ghostmas" instead of Halloween (which he hates) and constantly making use of a pair of tongs for a variety of purposes.