Spirou and the Mystery of the Zoo (Spirou et le Mystère du Jardin Zoologique in the original French) is a comic one-pager possibly written by Rob-Vel, and drawn by either him or Luc Lafnet. It features Spirou, Gertrude the Ostrich, Jacko the Parrot, Becar the Peacock and Mrs Encaissetou.
All the feathers in the Zoo of Anvers are going missing, be they on the rump of the birds or on the hats of the ticket-seller. Is Spirou involved? (Well, yes, obviously.)
Behind the scenes
This one-pager was released in July of 1938 in Le Journal de Spirou #15 in Belgium. It was reprinted in the Spirou par Rob-Vel collection of all of Rob-Vel's Spirou comics. It has not known an official English printing to this day.
Like many early Spirou one-pagers, it draws heavily from traditional Belgian folklore — in this case, the Gilles of the Carnival of Binges.