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

Marc Delarue as Romain

Diane Besnier as Laura