The tête à Toto is a French typographical design and children's game, well known to French schoolchildren.
It consists of the equation "0+0=0", written with the first two "0"s for eyes, the "+" for a nose, the "=" for a mouth, and the final "0" surrounding, as a stylized face or skull.
Zéro plus zéro égale la tête à Toto Zero plus zero equals the head of Toto (Toto's head) As his head equals zero, it means that his intelligence is null.
The name, or character, of Toto is a common stock character in French culture; he is the generic child used in jokes ("Toto asks his mother...").
See Blague de Toto (Toto joke).