They sure do grow up fast!

Harlow practiced standing with mom Nicole Richie’s help in a park in her Glendale, California, neighborhood Wednesday.

The infant — now nearly five months old — smiled and beamed while dad Joel Madden looked on.

I wonder when Nicole will have another baby. She has said that she wants five kids — specifically, twin boys and three girls.

Nicole Richie was out and about shopping for boyfriend and baby daddy Joel Madden’s 29th birthday.

The new mom, 26, hit up Alpha: Gear for Gents and a nearby party shop, where she bought balloons, party favors, a birthday banner and greeting cards that read, “Pushing 30” and “You’re the best dad ever — and I’m not pulling your leg.”

Nicole was wearing an “H” necklace in honor of her little daughter, Harlow.

Very sweet!

It seems that Nicole Ritchie and Joel Madden’s nanny for their newborn baby, Harlow Winter Kate Madden, must be raking in the overtime.   Having a newborn at home hasn’t stopped these two hard partying parents from stepping out on the town–a lot as of recently.

During the Grammys weekend, the couple went to several parties each night for hours. Last weekend, Richie and Madden once again left their tot at home to spend some quality time with Joel’s brother Benji and Lindsay Lohan at Teddy’s in the Hollywood Roosevelt Hotel. They didn’t rush home until the very end of the evening — “It’s almost as if they aren’t parents,” said a spy.

Nicole Richie and Joel Madden can’t stop gushing about their one-month-old daughter, Harlow, and Tom Cruise and Kate Holmes say that two-year-old Suri is “growing so quickly!”

When asked about Harlow at the Eli Broad Contemporary Art Museum in L.A. last night, a glowing Richie said, “She’s doing great!

“Really great, thank you!” added the 26-year-old, who looked slim and rested in a pale-colored dress.

Madden — who donned sneakers with his tux at the black tie event, and stayed arm-in-arm with Richie — chimed in: “Yeah, she’s good!”

Cruise and Holmes say that Suri is, “doing great!

“Yeah, that one I can keep going on about!” Cruise said.

And he’s not the only chatty one. “She’s talking a lot!” Cruise added.

“Every day she does something new,” Holmes, in sky-high gold heels and a strapless Lanvin dress, said. “She’s growing so quickly!”

Cruise said they see a lot of each other in Suri “24/7.”

So how are they spending Valentine’s Day?

“It will” be romantic, Cruise said, but remained mum when asked about the details: “I’m going to keep that to myself, but it’s going to be fun though!”

Also at the star-studded event: Christina Aguilera, in a bright blue curve-hugging blue dress, with beau Jordan Bratman —spending quality time together without new son Max.

After the museum opening, Richie and Madden hit up Clive Davis‘ Pre-Grammy party at the Beverly Hilton Hotel — but didn’t stay long.

“We have to get home!” Madden was overheard telling a friend at 11:40 p.m.. “She [Harlow] only sleeps three hours at a time. She’s with Grandma now, but if she wakes up…”

Nicole Richie and baby-daddy Joel Madden stepped out over the weekend.  Nicole Richie gave birth just TWO WEEKS ago and she is already back to being pin-thin.  Joel, however, seems to be packing on some pounds.  Look at his double chin!