A Shot in the Dark (1964, Peter Sellers, Elke Sommer)

"There's a Paris traffic scene in which a crowd on a RATP Renault peer down into Clouseau's Mini in which he and Sommer are stark naked. The bus is a TN series, and the last two digits of its fleet number are xx23, cut out, stencil-wise, on the rear platform valance." (thanks Mike Lloyd)