The much-travelled striker, who was given his first chance in league football by Holloway at Bristol Rovers in 1997. has become the Foxes boss's first signing since taking charge ast the Walkers Stadium in November.
Since then, the much-travelled Mullen has taken charge of clubs as diverse as Sligo Rovers in Ireland, Colwyn Bay in Wales and three non-League clubs in the Midlands - Market Drayton, Telford United and Bromsgrove Rovers.
Mr Sigg, who has travelled around much of China over the past quarter-century collecting its contemporary art, has yet to be convinced by all this talk of a boom in museums.