Ange Dargent

as Daniel Guéret, dit Microbe

Théophile Baquet

as Théo Leloir, dit Gasoil

Audrey Tautou

as Marie-Thérèse Guéret

Sacha Bourdo

as Le prof de russe

Fabio Zenoni

as M. Guéret

Laurent Poitrenaux

as Le dentiste

Étienne Charry

as L'organisateur du concours de dessin