What is the similarity between Bill Gates, Usain Bolt, Justin Timerblake and Ashwini Ponnappa? 

They have all embraced the ALS Ice-Bucket Challenge willingly.

Ashwini completed the challenge on Tuesday afternoon. She in turn issued a challenge to her doubles partner Jwala Gutta and former swimmer Rehan Poncha.  

After players and support staff of Bengaluru FC doused themselves in an icy-cold shower on Monday, they issued a 24-hour challenge to Sania Mirza, Ponnappa and Yuvraj Singh. 

After Sania completed the challenge on Tuesday morning, Ponnappa followed suit pretty soon. Both of them have uploaded the video on YouTube. 

Sania had already done the ice-bucket once before but since people complained that there was a lack of water, she did it again on Tuesday. 

She, in turn, challenged Cara Black, Mahesh Bhupathi, Yuvraj and actor Ritesh Deshmukh. 

What is the challenge exactly for? It raises money for charity -- especially ALS --- a neurodegenerative disorder.