Warren Buffett's 90th birthday is on Sunday. Here are 5 of the legendary investor's best birthday stories.

That ratio soared to 100% by the time he turned 74, the investor continued."Having discovered this mathematical relationship — let's call it Huggins' Law — Charlie and I now become giddy at the mere thought of Chuck's birthday," he joked.Buffett received a particularly nice birthday gift in 1983 when Mrs B, the 89-year-old owner of Nebraska Furniture Mart, agreed to sell the company to him."I think back to August 30, 1983 — my birthday — when I went to see Mrs B (Rose Blumkin), carrying a one and a quarter-page purchase proposal for NFM that I had drafted," he recalled in his 2013 shareholder letter. "Mrs B simply told me what was what, and her word was good enough for me."Buffett shared an example of Berkshire's "carefully crafted and sophisticated acquisition strategy" in his 1996 shareholder letter.The investor tried to get out of attending the 40th birthday party of his nephew's wife, Jane Rogers, but agreed to go after learning he would be sitting next to Jane's dad, Roy Dinsdale.During the party, Dinsdale revealed he had attended a directors' meeting at Kansas Bankers Surety, an insurance firm that Buffett had long admired.