Tonight, "Dancing With the Stars" Season 21 is celebrating its Most Memorable Year theme, with the celebs paying tribute to an important time or experience in their lives. Tom Bergeron will miss the show so he can spend memorable time with one of the most important people in his life: his father. Tom's father isill and the host is staying with him, so he'll miss the Fall 2015's season's fourth week of dancing:

Tom has been with the show since Season 1, unlike the many changing co-hosts around him, and his live quips have won him an Emmy and the affection of fans. People announce that Season 19 winner Alfonso Ribeiro will step in as host this week, alongside co-host Erin Andrews.

Alfonso was a guest judge on DWTS last week and he is the new host of Tom's "America's Funniest Home Videos," so it's no big surprise to see him back again. It's like he's slowly taking over!

But in all seriousness, fans are concerned about Tom and his dad and sent their love. Tom thanked viewers for their support:

It's been an emotional season so far, from Kim Zolciak being forced to withdraw last week, thanks to her mini stroke and doctor's no-fly diagnosis, and Alek Skarlatos returning home to Roseburg, Oregon after the mass shooting. (At least there was some good news: Pro dancer Witney Carson got engaged.) Here's hoping everyone stays safe this week, with best wishes to Tom and his father.

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