Yayoi Kusama takes a fabric, she stuffs it, hand-sews it, and then paints it. 

Repetition is her thing. She presents materials repetitively in all her paintings, drawings, sculptures, collages, and installations. And she does it with great charm. In this case, Kusama made hundreds of phallic bulges to make an armchair. She thinks it's funny, but in real life, people were shocked by her sexual humor. And indeed Kusama got bitter criticism from art critics of the '60s for it. Kusama couldn't care less. She would do it with anything from dildos to macaroni.
 
She's all about the process, less the outcome. Kusama said: "I make them and make them and then keep on making them, until I bury myself in the process. I call this obliteration." Which might be what happens to your private bits if you sit on this chair.