Princess Diana and Prince Charles
Princess Diana's wasn't that innocent at all according to the owner of the birthday card that the royal wrote for her accountant. Pictured: Princess Diana and Prince Charles at Westminster Abbey, London, for a centenary service for the Royal College Of Music on Feb. 28, 1982. Getty Images/Fox Photos

Princess Diana wasn't that innocent.

The late Princess of Wales' naughty and flirty birthday card to her accountant has resurfaced after it was put up for auction. Some found it rude and provocative, while others just thought it was hilarious as Princess Diana was popular for her playful nature. The owner of the card asked to remain anonymous, but shared his thoughts about the birthday card.

"I was shocked and surprised when I first saw the message in the card, because I always knew that Princess Diana had a cheeky sense of humour but I had no idea that it was to this extent," the owner told Mirror. "Her sense of humour was actually flirty and naughty judging by the text in this card."

The card owner explained that her gift was a testament to the late royal's true personality.

"I know that Diana liked to send humorous cards, but I haven't seen any quite this naughty, so for me it really shows that she was a fun human being that could share some dirty jokes with her closest friends," the owner added. "I also think that Diana wasn't that innocent at all! I mean, come on look at this card. She was quite the naughty Princess that wanted to cross boundaries and play on the dark side. This is a secret card that has been kept hidden for many years. A true gem for anyone that is a fan of this special human being."

The hilarious birthday card was addressed to Princess Diana's accountant and friend, Anthony Burrage. The cover features Sleeping Beauty with the words "A little prick in the hand sent Sleeping Beauty to sleep." Upon opening the card, the message read: "Only the big ones are worth staying awake for!...."

"Tony, A belated Happy Birthday for the 5th. Love, Diana," the People's Princess wrote.

The card's current owner reportedly got it from a collector of Princess Diana's things but decided to sell it with a starting bid at $197. The words in the card aren't shocking to those who personally know the late Princess of Wales' hilarious and naughty nature. Even Prince William and Prince Harry had their fair share of fun moments with their mom.

According to Paul Burrell, Princess Diana once gave Prince Harry a fake dog poop in his stocking. Royal chef Darren McGrady also shared that when the Duke of Cambridge turned 13, Princes Diana ordered a boobs cake for his son.