One must remain dignified and keep a stiff upper lip at all times, the age-old rules of royal etiquette must say somewhere. And absolutely no touching.

But even celebrities can slip up occasionally with all the excitement of meeting royalty. The same can also be said of certain members of the royal family. (We'relooking at you, Queen Elizabeth II.)

Here are 10 stars looking completely awestruck in front of Kate Middleton & Co., and vice versa.

1) Cara Delevingne meets Prince Charles and Camilla

Event, Yellow, Interaction, Fun, Ceremony, Gesture, Formal wear, Conversation, pinterest
Getty Images

Being spawn from aristocratic stock means Cara can guffaw as wide-mouthed and haughtily as she likes. (Plus, Camilla probably just shared a cracking gag.)

2) Reese Witherspoon meets Kate Middleton

Trousers, Dress, Coat, Waist, Ceremony, Necklace, Spring, One-piece garment, Day dress, Basket, pinterest
Getty Images

Kate's so getting an invite to Reese's place in the Hamptons.

3) Keanu Reeves meets Princess Beatrice

Event, Premiere, Facial hair, Smile, Suit, pinterest
Getty Images

Keanu's keeping cool as a cucumber (as usual), but Eugenie has gone as red as her frock. Not that we can blame her.

4) Beyoncé meets Kate Middleton

Hair, Face, Head, Camera, Video camera, Cameras & optics, Television crew, Tartan, Plaid, Film camera, pinterest
Getty Images

Queen Bey is basically royalty, so meeting the Duchess was no biggie.

5. LeBron James meets Kate Middleton and Prince William (and breaks the no-touching rule)

Yellow, Event, Fun, Facial hair, T-shirt, Outerwear, Beard, Smile, pinterest
Getty Images

Forget that he's clearly breaching protocol with the cozy hug — those sweat patches should not be touching that expensive, dry-clean-only coat ...

6) Leonardo DiCaprio and Princesses Beatrice and Eugenie

Clothing, Hair, Face, Coat, Trousers, Event, Dress, Shirt, Flooring, Outerwear, pinterest
Getty Images

A very, very young Leo looks completely nonplussed by meeting two princesses, but the same probably can't be said for Eugenie and Beatrice. (Watch that hand, Bea.)

7) Jennifer Garner meets Kate Middleton

Hair, Hairstyle, Brown hair, Long hair, Friendship, Shoulder, Interaction, Fun, Dress, Nightclub, pinterest
Getty Images

We've just found ourselves the perfect actress to play Kate Middleton in a future biopic.

8) Nicole Kidman meets Prince William

Hair, Coat, Trousers, Shirt, Outerwear, Dress, Suit, Formal wear, Collar, Bow tie, pinterest
Getty Images

"And my dance moves went a bit like this ... "

9) Tom Cruise meets Prince Philip

Clothing, Coat, Lighting, Collar, Shirt, Suit, Dress shirt, Outerwear, Formal wear, Blazer, pinterest
Getty Images

Chill out Cruise, it's not like you're meeting royalty or anything.

10) Jennifer Lopez and mother Guadalupe meets Kate and Wills

Event, Fashion, Fun, Party, Dress, Formal wear, Crowd, pinterest
Getty Images

Because even famous people can sometimes be a little embarrassed by their parents.

11) Kanye West and P Diddy meet Prince Harry

Event, Fun, Eyewear, Suit, Party, Formal wear, pinterest
Getty Images

We'd buy their music.

From: Cosmopolitan UK