Constant himself gave this work the title Visionaire stad (Visionary city) but when the work was exhibited at the Biennale in Venice in 1966 the work was titled Constructie met ladders.

Circa 1985. Waldo was Constant's second to last dog with whom he had an extraordinary relationship. According to Constant the dog was exceptionally cheeky and cute. Constant really admired this in him. Waldo's signature trick was that he could catch any ball you threw at him.

Constant exchanged the painting, Kat, 1949, with Tajiri's sculpture, Circus. Following documentation of the works in catalogs the exchange took place before 1962. Circus is documented in Cobra, Journaal van de Nederlandse musea voor moderne kunst in 1962 as belonging to the collection of Constant.*

In the 1980 exhibition catalog nr. 39 of Constant. Schilderijen 1940-1980 the date on the painting Kat is "1950" not "1949". The photo in the catalog was taken by Victor Nieuwenhuys, Constant's son. In the 1965 catalog nr. 30 of Constant the painting Kat is dated "1950", coll. S. Tajiri, Baarlo, L. Restorer Marjan de Visser recognised Constant's hand in the date change when she restored the painting in 2015. We have no documentation on why the date was changed and when.

*Source: Troels Andersen, Christian Dotremont, Gerrit Kouwenaar, J. Martinet, J. Eijkelboom en Wim Beeren, Cobra, Journaal van de Nederlandse musea voor moderne kunst, januari/februari 1962 – serie 7 no 7/8, afb. p. 188 [Tajiri, Circus 1952, Coll. C. Nieuwenhuys, Amsterdam].

A small printed booklet with poetry by Gerrit Kouwenaar and drawings by Constant. They created it in 1949 and it was supposed to be a little joke. This is also one of the lines in the booklet: 'Everyone considers themself to be a joke. A joke is allowed' (Elk voelt zich een grapje, een grapje dat mag) The words and drawings are an expression of the playfullness of their creators where sometimes the words came first and the drawings followed as a reaction and sometimes the other way around.