YOU SAID:
People in pizza slice costumes becoming pizzas
INTO JAPANESE
ピザスライスの衣装を着た人々がピザになります
BACK INTO ENGLISH
People wearing pizza slice costumes become pizza
INTO JAPANESE
ピザのスライスの衣装を着た人はピザになります
BACK INTO ENGLISH
Anyone in a pizza slice costume will be a pizza
INTO JAPANESE
ピザスライスの衣装を着た人は誰でもピザになります
BACK INTO ENGLISH
Anyone wearing a pizza slice costume will be a pizza
INTO JAPANESE
ピザのスライスコスチュームを着ている人は誰でもピザになります
BACK INTO ENGLISH
Anyone wearing a pizza slice costume will be a pizza
That didn't even make that much sense in English.