Comedians James Corden, Seth Meyers, Jimmy Kimmel, Jimmy Fallon and Stephen Colbert all said their congratulations in between cracking jokes. But Kate will always have time to share advice with her pregnant sister Pippa Middleton.
We're just waiting to hear his name...
Snuggled up in a white knit hat and a matching white shawl, which are from design house GH Hurt & Son Ltd., the baby looked totally unperturbed by the hundreds of waiting photographers and screaming fans.
Officials announced her previous pregnancies before the traditional 12-week mark because she was too unwell to attend public engagements.
Arthur, Albert and Jack are among the bookmakers' favourite names for the boy, who is the couple's heaviest child at birth. They're called gambling addicts.
The new royal baby bears a striking resemblance to his siblings.
Prime Minister Theresa May congratulated Kate and William on Twitter. "I'm sure it was exhausting. I would prefer to be at a palace rather than a hospital as well". She also looked sensational. But perhaps that's why I love her so darn much. The Duchess safely delivered a boy at 11:01 am, weighing 8lbs 7oz, who will be fifth in line to the throne. "St. George himself would be very pleased if the baby's born today". "A title previously held by Prince Chubbington NoNeck III". The royal mom opted for dresses by Jenny Packham for her first two births as well.
"That guy is just some guy". For the British royal family, keeping the baby's gender a secret is protocol. "But he's easy to mistake for royalty: He's got a stupid hat, and he doesn't have a real job".
By now, the parents of three are "absolute pros" when it comes to raising kids, a source told Us Weekly in March.
"Obviously she has pressures that she's taken on and things, but we spend a lot of time together".