 Following the closure of the season, the Top Ten dancers often go on tour for several months, performing hit routines from the season among other performances.A typical season of "So You Think You Can Dance" is presided over by a panel of 2–4 permanent judges, supplemented by occasional guest judges, with the panel sometimes ballooning up to twice or more its normal size for callback episodes or season finales.Executive producer and co-creator of the show Nigel Lythgoe is the only judge to have sat as a permanent member of the panel across all seasons, although ballroom specialist Mary Murphy has also sat as a permanent member of the panel for the majority of seasons.