Vanessa Hudgens and Ashley Tisdale have been the definition of friendship goals for the past 11 years, since fans first fell in love with High School Musical's sweet Gabriella Montez and sassy Sharpay Evans. After making three HSM films, touring the world, playing Catholic schoolgirls on The Suite Life of Zack and Cody, releasing new solo music, and continuing to work in the same fickle industry, the duo have remained BFFs.

In honor of their friendship, let's take a look at what helps the besties stay besties.

They are each other's biggest stans

Tisdale also urged fans to support her bestie during Grease: Live, offering Hudgens "prayers of strength" after losing her father the day before performing.

And always remember the other's birthday

As someone who just combed through their collective 3,794 (and counting!) Instagram pics, I can confidently tell you they're loyal birthday wishers — and in an era when we tend to rely on Facebook to "remember" friends' birthdays, this speaks volumes.

They're not afraid to laugh at one another

Or proudly name the other #WCW

They keep each other's legacy alive

Recently, Tisdale revealed one of the eyeshadow names from her Illuminate collection to be "Nessa," a.k.a. Vanessa Hudgens.

And never forget their roots

Tisdale's caption comes from her High School Musical song, "Bop to the Top." Hudgens shared the same pic with the caption, "Muy caliente😉," also from the song.

They know how to get down and let off steam

If you're not throwing a Victoria's Secret Fashion Show party with onesies, cookies, and Emily Osment, then are you really even friends? The duo also jam out to Selena Gomez, so your argument is invalid.

They quote Bridesmaids with style

And rock out with Guitar Hero

They make time to hang out on Halloween

Complete with Tisdale's dog, Maui.

And support each other's love lives

Hudgens was a bridesmaid in Tisdale's wedding to Christopher French in 2014. Meanwhile, Tisdale is BFFs with Hudgens's boyfriend, Austin Butler.

But, most importantly, they duet together

After being denied a Gabriella/Sharpay duet in all three High School Musical films, Hudgens stopped by Tisdale's "Music Sessions" YouTube series to cover Elle King's "Ex's and Oh's." #bless