When measuring a statistic from a galaxy survey, it is important to be able to test different methods for measuring the statistic and for removing various systematic effects. Mock galaxy catalogues are extremely useful for this purpose since the value which would have been measured by the survey can be compared with the 'actual' value from the mock catalogue. With upcoming galaxy surveys such as DESI and Euclid, it is therefore important to be able to make realistic mock catalogues. In this talk I will outline our method for creating a mock catalogue from the Millennium-XXL (MXXL) simulation. We use a halo occupation distribution (HOD) scheme to populate dark matter haloes from the simulation with galaxies, assigning each galaxy a r-band magnitude and g-r colour. This is based on the method of Skibba et al 2006 and Skibba & Sheth 2009, but extended to add scatter to the luminosity of central galaxies and to include galaxy and clustering evolution.