Here is the full list of all 8 Pet achievements.
You left without going up to the vending machine.
You went to the vending machine, but you didn't meet anyone.
You went to the vending machine, and you met someone.
Someone got a new pet.
I'll always love you for taking care of me.
You emptied the whole machine.
You already made your decision.
You picked the wrong path. Maybe on purpose.