But the 43-year-old singer-actress doesn't mind one bit! In fact, she's laughing right alongside Joan, 80, on Friday's episode.
"You look better than I thought you were gonna look," Joan says candidly.
Jennifer laughs and claps bemusedly, but seemingly understands what Joan means, saying, "You never know what's gonna walk in!"
"You walked in and I thought Aubrey Hepburn," Joan says. "You didn't come in like Chiquita banana! You walked in like a star."
But J.Lo didn't always feel like the glam Hollywood beauty we know her as today. Growing up in the Bronx, it was her sister Linda who was "the beautiful one."
"She looks very skinny and tall and I'm the opposite," Jennifer says, adding laughingly, "I'm like short and stout!"
So what was young J.Lo like in those early days? "I was the athletic one," she says.
But her modest upbringing still helps her to stay grounded today. "I think when you grow up how I grew up…you never take it for granted," she explains. "You're always like looking around like, 'Wow, this is a lot of shoes!'"
"It never gets old for me," she goes on. "Just like it never gets old the first day on the set of a film. It never gets old the first time I hear my new record on the radio…It means something to me. I'm very grateful."
That said, Jennifer's the first to admit she's had various highs and lows in her professional life. "But any normal career's like that," she says. "You really learn a lot. But you learn a lot in those low moments, and you come out stronger and better and able to do more. I get a lot of joy in that. I get a lot of joy in, you know, just being here."
"Thank you for all the love on the show," she gushes to Joan. "And even when you give me the jabs, I like that, too."
Yep, Jenny from the block can still take a joke!
For more J.Lo, tune in to Fashion Police Friday at 10 p.m. on E!