YOU SAID:
I have a cat in my pants
INTO JAPANESE
私はズボンに猫がいる
BACK INTO ENGLISH
I have a cat on my pants
INTO JAPANESE
私は私のズボンに猫を持っています
BACK INTO ENGLISH
I have a cat in my pants
INTO JAPANESE
私はズボンに猫がいる
BACK INTO ENGLISH
I have a cat on my pants
INTO JAPANESE
私は私のズボンに猫を持っています
it is unlikely that this phrase will ever reach equilibrium