People baffled after realizing Jerry Seinfeld is now older than Billye Ree Wallace when she starred as his nana on show

Jerry Seinfeld turned 70 this week, and TV fans have been left in shock as they realised that now makes him older than his on-screen 'Nana'.

The sitcom, which ran from 1989 until 1998, followed stand-up comedian Seinfeld alongside his New York pals.

This year, the show ended up making Seinfeld a billionaire, though he turned down an offer to return for a tenth season despite a massive pay increase.

Actress Billye Ree Wallace was a secondary character, playing Jerry's grandmother in the series.

Jerry Seinfeld at the premiere of Netflix's Unfrosted last month (Charley Gallay/Getty Images for Netflix)

In the 80s and 90s, when the series aired, she was thought to be in her 70s, but Wallace would have actually been 64 when she played the role, making her younger than Seinfeld is now.

The ages add up, but people on Reddit have been left scratching their heads as they work it out.

A post with a meme showing Nana, reads: "Jerry Seinfeld turns 70 today. If that's not mindblowing enough, he is now older than Billye Ree Wallace was when she played his Nana in Seinfeld.

Writing on the Reddit thread, one person replied: "Weird to me how people just used to look older at the same age compared to now."

Reddit users have been left baffled by the realisation that Jerry Seinfield is now older than 'Nana'. (Reddit)

Another shared: "I had no clue he was in his 40s for half the show."

"Nana was a good character but that casting made no sense. Her 'kids' Helen and Leo were the around the same age as her," pointed out a third.

A fourth added: "How do older generations look so much older than current generations at the same age?"

To which someone replied: "That’s a good question…. Me and peeps are all in our early 50s and we passing for 30s… and remembering when we were in our 20s how 50 year olds looked ancient."

Seinfield ran from 1989 until 1999. (Castle Rock Entertainment/Sony Rock Pictures)

Another person asked: "How old was she in the show? She looks older than 70."

Whilst another added: "No way that old sweet lady was younger than 70."

Outside of her role in Seinfeld, Billye Ree Wallace also starred in ER and Night Visitors. She also played spirited old ladies in sitcoms such as Dream On, Coach, Ellen and Who’s the Boss?

Wallace died on March 3 1999 in Los Angeles, California, USA aged 73 of respiratory failure and emphysema at Cedars-Sinai Medical Center.