Why was Matt LeBlanc on stage at a Taylor Swift concert?

It's an excellent question and one of the many that have surfaced since Swift started touring the world in support of her quintuple-platinum "1989" album. The pop mega-star has always made a habit of inviting an eclectic group of celebrity guests on stage at her concerts, but this year, she has raised the bar with a barrage of singers, supermodels, athletes, A-list actresses and famed '90s sitcom stars. Some perform, some just stand on stage and wave. Not only is it a treat for the audience, but it serves the guests very well. After all, history shows that being associated with Swift can greatly impact your celebrity status.

It's a lot to process, so here's a complete guide to the guests on Swift's tour - and why these stars were the chosen ones.

Las Vegas, May 15

Musical guest:

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Ed Sheeran

Song:

Tenerife Sea

Why was Sheeran there?

Swift and Sheeran go way back, from that time they wrote her single

Everything Has Changed

on a trampoline. Plus, he was an opener on her

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tour.

Swizzle

A video posted by @teddysphotos on

Detroit, May 30

RAGE FEST with Dan Reynolds from Imagine Dragons. #radioactive #1989TourDetroit

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Dan Reynolds of Imagine Dragons

Celebrity guests:

Martha Hunt, Gigi Hadid

Song:

Radioactive

Why was Reynolds there?

Imagine Dragons is one of her favorite bands, as she told the crowd.

Why were Hadid and Hunt there?

Both model squad members and co-stars in the

Bad Blood

video, Hadid is also dating Swift's ex-boyfriend, Joe Jonas.

Pittsburgh, June 6

Tonight my friends @littlebigtown surprised the #1989TourPittsburgh crowd with 'Pontoon' and it was SO MUCH FUN!!

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Little Big Town

Song:

Pontoon

Why were they there?

Swift is still a Nashville gal at heart.

Philadelphia, June 12

Syd and me tonight. @Echosmith #1989TourPhilly

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Echosmith

Celebrity guests:

Cara Delevingne, Mariska Hargitay

Song:

Cool Kids

Why was Echosmith there?

Swift and lead vocalist Sydney Sierota became pals at the 2014 VMAs.

Why were Delevigne and Hargitay there?

Delevingne is a longtime member of the #squad; Swift is a huge

Law & Order: SVU

fan, and one of her cats is named after Hargitay's character, Olivia Benson.

Philadelphia, June 13

...and I've still got a lot of fight left in me. @rachelplatten #1989TourPhilly

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Rachel Platten

Celebrity guest:

Mariska Hargitay

Song:

Fight Song

Why was Platten there?

Swift bonded with Platten backstage a few nights earlier in Pittsburgh singing this inspirational tune.

Why was Hargitay there?

See above.

London, June 27

The squad in London. @caradelevingne @kendalljenner @gigihadid @marhunt @serenawilliams @karliekloss

A photo posted by Taylor Swift (@taylorswift) on

Celebrity guests:

Cara Delevingne, Gigi Hadad, Martha Hunt, Kendell Jenner, Karlie Kloss, Serena Williams

Why were they there?

All squad members, except for Serena Williams, who was in town for Wimbledon.

East Rutherford, New Jersey, July 10

I was so honored to share the stage with The Weeknd tonight! @abelxo #1989TourEastRutherford

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

The Weekend

Celebrity guests:

Lily Aldridge, Lena Dunham, Gigi Hadid, Heidi Klum, Hailee Steinfeld, U.S. women's soccer team

Song:

Can't Feel My Face

Why was The Weeknd there? Well, they do share a producer in Max Martin.

Why were all those other people there?

It's a good number of

Bad Blood

video stars and friends, plus Klum, who likely felt right at home among fellow supermodels Aldridge and Hadid. Oh, and the women's soccer team had just won the World Cup.

East Rutherford, New Jersey, July 11

Last night the incredible @nickjonas sang 'Jealous' and 60,000 people sang it with us/screamed uncontrollably.

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Nick Jonas

Celebrity guests:

Uzo Aduba, Lily Aldridge, Gigi Hadid, Martha Hunt, Karlie Kloss, Behati Prinsloo, Candice Swanepoel

Song:

Jealous

Why was Jonas there?

Swift and the JoBros have known each other for years; he also dated her BFF Selena Gomez.

Why was everyone else there?

Some repeats from the night before, with the addition of some more supermodel friends and Uzo Aduba from

Orange is the New Black

. (Maybe Swift is a Netflix binge-watcher?)

Washington, D.C., July 13

Musical guest:

Lorde

Song:

Royals

Why was Lorde there?

Lorde & Taylor: A well-documented Insta-friendship.

Washington, D.C., July 14

Musical guest:

Jason Derulo

Song:

Want to Want Me

Why was Derulo there?

Swift told the crowd it's one of her favorite summer songs.

Chicago, July 18

Later on, when @serayah slayed it on stage singing 'Style' with me at Soldier Field in Chicago....

A photo posted by Taylor Swift (@taylorswift) on

Musical guests:

Andy Grammer, Serayah

Song:

Honey, I'm Good

Why was Grammer there?

This is his second appearance on a Swift tour - he showed up a couple years ago to play

Keep Your Head Up

, Swift's favorite song when she's having a bad day.

Why was Serayah there?

A fairly new edition to the squad, the 20-year-old

Empire

star helped Swift out on vocals during

Style

.

Chicago, July 19

A huge thank you to @SamHuntMusic for surprising the crowd with 'Take Your Time'. Such a star. #1989tourchicago

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Sam Hunt

Celebrity guests:

Lily Donaldson, Andreja Pejic

Song:

Take Your Time

Why was Hunt there?

Swift likes to keep tabs on the Nashville scene. Before their flirty duet, she called him "the coolest new thing that country music has going on."

Why were Donaldson and Pejic there?

Because Swift really, really likes having supermodel friends?

Foxborough, Massachusetts, July 24

Thanks @WALKTHEMOONband for surprising the Boston crowd with 'Shut Up and Dance'!!! 60,000 person dance party.

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Walk the Moon

Song:

Shut Up and Dance

Why was Walk the Moon there?

Released last year, it's still a contender for song of the summer.

Foxborough, Massachusetts, July 25

Musical guest:

MKTO

Song:

Classic

Why was MKTO there?

Because it's the catchiest song ever and earworm expert Taylor Swift knows it.

Vancouver, Aug. 1

Me having no chill at all at sound check with @nicoandvinz

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Nico & Vinz

Song:

Am I Wrong

Why were Nico & Vinz there?

Swift is OBSESSED with them.

Seattle, Aug. 8

Musical guest:

Fetty Wap

Celebrity guests:

Ciara, Russell Wilson

Song:

Trap Queen

Why was Fetty Wap there?

Another song of the summer contender.

Why were Wilson and Ciara there?

Swift likes to bring out hometown stars (Wilson is a favorite of the Seahawks) and he and Ciara are one of this year's most-talked about couples.

Santa Clara, California, Aug. 14

So stoked this pic exists because this was SO MUCH FUN @FifthHarmony

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Fifth Harmony

Song:

Worth It

Why was Fifth Harmony there?

Swift has been good friends with group member Camila Cabello for awhile, which she proved by borrowing one of Fifth Harmony's outfits for the performance.

Santa Clara, California, Aug. 15

Tonight Joan Baez and Julia Roberts danced it out to 'Style'. These two women are my heroes. What an honor.

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Little Mix

Celebrity guests:

Joan Baez, Julia Roberts

Song:

Black Magic

Why was Little Mix there?

They were already nearby for the Teen Choice Awards in Los Angeles. Oh, and group member Perrie Edwards used to be engaged to Zayn Malik, the ex-One Direction star, and Swift also used to date Harry Styles.

Why were Roberts and Baez there?

Your guess is as good as ours - though Swift did call the women two of her heroes.

Los Angeles, Aug. 21

Musical guest:

Ryan Tedder

Celebrity guest:

Kobe Bryant

Song:

Counting Stars

Why was Tedder there?

He co-wrote two tracks on

1989

(

Welcome to New York

and

I Know Places

) so it was only fair.

Why was Bryant there?

In a twist, the Lakers star was there to surprise Swift: He presented a new Staples Center banner that congratulated her on being the artist with the most sold-out concerts ever at the venue.

Los Angeles, Aug. 22

Musical guests:

Mary J. Blige, Uzo Aduba

Celebrity guests:

Matt LeBlanc, Sean O'Pry, Chris Rock

Blige's songs:

Doubt

,

Family Affair

Why was she there?

Swift says she was very inspired when she heard Blige sing

Doubt

at a pre-Grammy party last year, and also wants no more drama in her life.

Aduba's song:

White Horse

Why was she there?

Aduba (a guest earlier in the summer in East Rutherford) told Vulture she got a message from Swift inviting her to sing on stage. Who would turn that down?

Why were LeBlanc, O'Pry and Rock there?

Swift is a big fan of

Friends

. We know Rock is a big fan of Swift. And Sean O'Pry was the star of Swift's

Blank Space

video.

Los Angeles, Aug. 24

Alanis singing 'You Oughta Know' last night was something I'll never forget. I loooove her.

A photo posted by Taylor Swift (@taylorswift) on

Musical guest:

Alanis Morissette, Natalie Maines

Celebrity guest:

Ellen DeGeneres

Maines' song:

Goodbye Earl

Why was she there?

Swift used to perform Dixie Chicks songs at all her school talent shows, so may as well bring it to a bigger stage.

Morissette's song:

You Oughta Know

Why was she there?

It's one of the most famous songs about an ex-boyfriend, a theme Swift knows very well.

Why was DeGeneres there?

The two have been buddies for years, with Swift a frequent guest on her talk show - even though Ellen often tries to freak her out.

Los Angeles, Aug. 25

ALL OF ME. JOHN LEGEND. ALL THE FEELS.

A photo posted by Taylor Swift (@taylorswift) on

Musical guests:

Beck, St. Vincent, John Legend

Beck's song:

Dreams

, with St. Vincent on guitar

Why were they there?

St. Vincent is dating Swift's squad member Cara Delevigne; Beck has a new single.

Legend's song:

All of Me

Why was he there?

According to Swift, she heard Legend and his wife, Chrissy Teigen, were on their way to the show - so she called and asked about an impromptu performance.

Los Angeles, Aug. 26

Justin Timberlake. Mid-mic drop. #1989TourLA

A photo posted by Taylor Swift (@taylorswift) on

Musical guests:

Justin Timberlake, Selena Gomez

Celebrity guest:

Lisa Kudrow

Timberlake's song:

Mirrors

Why was he there?

The former 'N Sync frontman was one of Swift's first celebrity crushes before she became a superstar - now he joins her on stage and shows up at her 25th birthday party.

Gomez's song:

Good For You

Why was she there?

The two have been best friends for a long time, even though Swift is rightly repulsed by Gomez's on-again off-again romance with Justin Bieber.

Why was Kudrow there?

To sing

Smelly Cat

from

Friends

- that's right, Swift's powerful enough to get an Emmy-nominated actress to reprise a decades-old sitcom role.

San Diego, Aug. 29

Taylor hearts Avril. ??

A photo posted by Taylor Swift (@taylorswift) on

Musical guets:

Avril Lavigne, OMI

OMI's Song:

Cheerleader

Why was he there?

It's another song of the summer contender.

Lavigne's song:

Complicated

Why was she there?

To quell the notion that the two are in a feud. People tried to stoke the fire when Swift "liked" a Tumblr post that implied Lavigne wasn't friendly to her fans - but Swift is way too savvy for that story to blow up.