'Dancing With the Stars' Contestants Amy Purdy, Danica McKellar Give Emotional Performances

ABC/Adam Taylor
Danica McKellar and partner Val Chmerkovskiy

Meanwhile, Billy Dee Williams announces he's bowing out because of a back issue.

The contestants recalled their most memorable life experiences on Monday's Dancing With the Stars, prompting both touching moments and high scores from the judges.

The emotionally charged episode was a fitting night for guest judge Robin Roberts to join the panel, and the Good Morning America host had plenty of positive comments for the contestants. 

Paralympian snowboarder Amy Purdy had one of the most touching stories of the night as she recalled when she was first diagnosed with meningitis in 1999. 
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"I was 19 years old, and that’s when my life changed forever," said the double amputee. "I ended up losing my legs and my kidney function. That's also the year my dad gave me one of his kidneys.

"I remember standing in my new legs for my first time, and they were so painful, then some music came on," she went on to reveal, and she eventually came to the brave conclusion that "If I can dance, I can walk. If I can walk, I can snowboard."

Purdy and partner Derek Hough tried out a new pair of prosthetic legs for episode three of the dance competition, which allowed her to be on her toes the entire time in a pointed position. 

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"The choreography of this dance tells the journey of what I went through. My falling and my dad catching me," explained Purdy after their dance brought a stunned silence followed by an explosion of applause.

"There won't be a dry eye in the country tonight. Borderline immaculate," praised judge Len Goodman, while Roberts said: "There are not enough superlatives. I hope you know what you are doing for people."

There were many more touching moments in the special episode, which included NeNe Leakes having partner Tony Dovolani strip to show his rippling  abs. "Now you can go eat and stop doing those crunches, Tony," joked co-host Erin Andrews, as he flexed his six-pack. 

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Cody Simpson recalled moving to the U.S. from Australia, so he danced to "Surfboard" to remember surfing with his dad.

"So refreshing, so right here, so right now," gushed judge Bruno Tonioli. "There was no wipeout -- well done!"

Former Wonder Years star Danica McKellar and her partner, Val Chmerkovskiy, went on to do an angelic performance in white. "It was a beautiful way to express a meaningful story," said the judges, while it was described lushly as "like butter on warm toast."

Meanwhile, after battling diabetes, Drew Carey revealed that he lost weight for his son, Connor, before taking to the floor for a waltz, which was described by Goodman as a "charming dance" despite getting on the wrong foot.

"I think he did really good, and I need her to teach me some of those moves," said Connor cheekily while flirting with Carey's partner, Cheryl Burke

Sadly, Monday's installment also bid farewell to Star Wars actor Billy Dee Williams, who had to retire because of a back issue. "I've had a wonderful, brilliant, fantastic, blast of a time," said the 76-year-old, as he said good-bye to partner Emma Slater.

Roberts is the first of many celebrity guest judges to come, including Julianne Hough, Ricky Martin and LMFAO's Redfoo