Muslim “Not normal”

A Muslim family on the quays of Evian: one of them bears this strange and mysterious inscription: “not normal”

Walk on the quays of Evian (Haute-Savoie - France): but why this “not normal” inscription? This is the only time I came across this Muslim family (which are relatively numerous in summer) and who seem very interested in the black-headed gulls.... (french "mouettes rieuses", laughing gulls).