Funny sarcastic happy birthday wish カード

You're not old until you hear the fat lady sing, reads the front of this hilarious birthday greeting card, designed for the brother, sister, cousin, BFF, or anybody who is fond of teasing their sibling, BFF, etc. about their age or growing older. The outside makes an offhand compliment while the inside tramples it underfoot with the words "Doesn't she have a lovely voice." Surely the recipient will find it super funny even if he or she doesn't agree with the sneaky implication.