I got a fitness coach who helped me work much harder and I also wanted to deal with my voice, my speech, because I used to speak very slowly with my stammer.

Source: https://www.independent.co.uk/sport/football/dayot-upamecano-bayern-interview-champions-league-b2280864.html

In the docu-series, the global megastar Shah Rukh Khan talks about how he perfected his stammer in Darr and reveals how he used to bounce off crazy ideas to nail his villainous act in the Yash Chopra blockbuster!

Source: https://www.koimoi.com/bollywood-news/shah-rukh-khan-opens-up-about-how-he-perfected-his-stutter-in-darr-i-only-stammer-on-the-word-kirron/

She also developed a stammer, for which she was treated unsuccessfully by Lionel Logue, King George VI's speech therapist.

Source: https://www.dailymail.co.uk/femail/article-11880951/Unseen-picture-Dirty-Duchess-Argyll-display-National-Portrait-Gallery.html?ns_mchannel=rss&ns_campaign=1490&ito=1490