i couldn't give a rat's ass
I don't care.
I couldn't give a rat's ass about birthdays.
i couldn't give a rat's ass
An expression meaning I couldn't care a less or give a shit about something.
Worker: "I was late to work because my car broke down goddamit!"
Boss: "I couldn't give a rat's ass if you got anally raped this morning! You're fired!"
Boss: "I couldn't give a rat's ass if you got anally raped this morning! You're fired!"