Good news! A source at So You Think You Can Dance tells us that Katie Holmes is indeed planning to appear on the show.

"As far as I know, that's the plan," says the source, who also says that the extravagant affair is not for this week's episode, but could not confirm it's for the 100th episode as rumored. Our source adds that there are many dancers on the set today rehearsing for a big performance, including many SYTYCD alums.

Meanwhile, X17 caught show producer and judge Nigel Lythgoe over the weekend to get the dirt. Click on to watch video of that...