Comedian Danny DeVito's fantastic performance as the bizarre but likable Frank Reynolds on the hilarious comedy sitcom It's Always Sunny in Philadelphia has helped skyrocket the show's popularity and success thanks to the character's unique strangeness and endlessly quotable one-liners.

Debuting in the season 2 opener, Frank has since become a cherished fan favorite amongst audiences as he became responsible for many of the show's most iconic and laugh-out-loud moments. Some of the best interactions with Frank sometimes occurred even before the opening credits started to appear. Here are ten of Frank's best cold opens that helped jump-start these episodes on a hilarious high note.

10 Frank gives presents to himself - "A Very Sunny Christmas" (Season 6, Episode 13)

A Very Sunny Christmas (Season 6, Episode 13)

It's Christmas in Philadelphia, and the Gang is trying to seem cheerful during the holiday season. However, Dennis (Glenn Howerton) and Dee (Kaitlin Olsen) aren't too happy when they see their former father-in-law Frank arrive on the scene, decked out with luxurious gifts all for himself that the two always wanted.

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As Frank awkwardly stepped out of his expensive Lamborghini in his yellow jumpsuit, audiences knew they were in for a wild and hysterical Christmas-themed episode. This opener greatly sets up the comedic tone and how Frank's wacky antics would take center stage during the Gang's holiday celebration.

9 Frank's Introduction - "Charlie Gets Crippled" (Season 2, Episode 1)

Frank's first episode on 'It's Always Sunny in Philadelphia'

The four original members of the Gang try to hastily leave the bar to avoid Frank, who's arriving determined to rekindle his relationship with his estranged children, Dennis and Dee. However, during their escape, Frank appears right in front of Dennis' car, startling him into accidentally backing the vehicle right into Charlie (Charlie Day.)

What better way to make an entrance than to appear straight out of nowhere and immediately causing trouble? This introduction, while very brief, sets up Frank to be a new and interesting addition to the group's dynamic while also foreshadowing his eventual mischievous behavior.

8 Frank gets ready for the day - "Being Frank" (Season 11, Episode 6)

Frank in It's Always Sunny In Philadelphia

Ever wondered what it's like in a day in the life of Frank Reynolds? After another night of heavy partying, Frank awakens from his drunken stupor to find Dennis summoning him for one of the Gang's next big schemes. Despite being barely conscious, he eventually gets ready to take on the day.

In an interesting visual style change for the show, this opener, along with the entire episode, is shown entirely through Frank's point of view as he goes through the day and interacts with one of the Gang's many schemes. It also offers insight into Frank's thought process, how he views each member of the gang and how he tries to help in any way he can.

7 Frank and Charlie: Sewer Dwellers - "Dee Gives Birth" (Season 6, Episode 12)

It's Always Sunny "Dee Gives Birth" (S 6, E 12)

Frank and Charlie reveal to the group that they've shockingly found hundreds of unopened mail that Dee has been tossing away while they were rooting around in the sewers. However, Dennis and Mac (Rob McElhenney) are more interested and disgusted by the fact that the two men are just casually hanging out in the dark and disease-infested sewers for fun.

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"The Gruesome Twosome" is on full display in this opener, as Frank and Charlie's bizarre co-dependent friendship has gotten the two into another one of their awkward and ridiculous situations. DeVito's and Day's abilities to keep straight faces as their characters just casually address that they roam around in sewers is both hilarious and an impressive display of the two comedic stars acting talents.

6 Frank wants to marry Roxy - "Frank's Pretty Woman" (Season 7, Episode 1)

Frank and Roxy in 'It's Always Sunny in Philadelphia'

The Gang becomes very uncomfortable when Frank begins a romantic relationship with a highly crass sex worker named Roxy (Alanna Ubach.) However, things become even more complicated as Frank plans to make Roxy his new wife.

From his turbulent marriage with his deceased ex-wife Barbara (Anne Archer) to his on-again, off-again relationship with Dee's free spirited-friend Artemis (Artemis Pebdani), it's clear that Frank's history with relationships has become complex. However, his brief but somewhat heartfelt relationship with Roxy in this opener and episode overall is a genuinely interesting concept as their romance shows Frank in a slightly more sensitive and positive light.

5 Frank hits Dennis' car - "Reynolds vs. Reynolds: The Cereal Defense" (Season 8, Episode 10)

Glenn Howerton eating cereal in his car in 'It's Always Sunny in Philadelphia'

Frank's declining memory has now forced him to rely on Charlie's homemade navigational tapes to direct him to the Gang's bar "Patty's Pub." However, when he becomes distracted one day while fixing one of these tapes on the road, he accidentally rear-ends Dennis' jeep who was driving to work with a bowl of cereal in his hands.

It's a strange but memorable opener that shows how Frank's confusion and recklessness cause more unintentional mayhem than usual. It's also a fascinating introduction for a fun episode that sees Frank and Dennis battling each other to decide who pays for repairs since the only damages to Dennis' car were the result of him spilling his cereal during the crash.

4 The Wolf Cola incident - "Wolf Cola: A Public Relations Nightmare" (Season 12, Episode 4)

It's Always Sunny in Philadelphia, Wolf Cola: A Public Relations Nightmare

When his sham money laundering front company "Wolf Cola" becomes a massive seller in Boca Raton, Florida, Frank begins to celebrate his newfound business success in style. Unfortunately, though, he later discovers that, in a lapse of judgment, he misread the buyer's name and unintentionally sent his products to be endorsed by a hostile terrorist organization.

Frank has made plenty of mistakes throughout the years during his business ventures, but confusing a terrorist group based in Africa for a beach town in Florida ranks pretty high on the list of worst foul-ups anyone could ever make. This scene hilariously conveys to the viewers that when Frank Reynolds makes a mistake, he does so in a spectacular fashion.

3 Frank "Mourns" for his Ex-Wife - "Dennis and Dee's Mom is Dead" (Season 3, Episode 3)

'It's Always Sunny in Philadelphia' Season 3, Episode 3 - Dennis and Dee's Mom is Dead

Frank enters the bar celebrating with his exciting announcement that his scornful ex-wife Barbra has died during a botched surgery. While Barbra's children, Dennis and Dee, are visibly shocked by this terrible news, Frank instead decides to relish the moment by lighting up a cigar and offering everyone some Champaign.

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Leave it to Frank to turn a serious and dramatic revelation into a darkly comedic situation. His apathetic and cheerful attitude at the realization that his ex-wife has passed indicates that their complicated marriage was a match made in Hell.

2 Frank's living on the edge - "The Gang Gives Frank an Intervention" (Season 5, Episode 4)

'It's Always Sunny' "The Gang Gives Frank an Intervention"

Frank, for no particular reason, decides to spiral out of control on a booze-fueled mission to become as extremely gross and depraved as possible. The Gang, for the most part, support his antics, until Frank tricks them by taking the Gang to a beach party, only for the party to be revealed to be Dennis and Dees' Uncle's funeral.

It's an iconic start to an iconic episode that highlights DeVito's comedic acting chops and the character's memorable weirdness. From start to finish, this scene lets the viewers know that Frank is hitting rock bottom but enjoying every moment of it.

1 Frank goes live on the air - "Gun Fever Too: Still Hot" (Season 9, Episode 2)

Danny DeVito as Frank in 'It's Always Sunny' S9 E2 "Gun Fever Too: Still Hot"

After scaring off several muggers on the streets using a few of his unregistered firearms, Frank becomes a local hero and goes on a live news broadcast to recount his harrowing ordeal. However, the interview quickly devolves into absurdity when Frank pulls out the same two handguns as part of a much-unneeded visual demonstration.

Viewers unfamiliar with the show could look to this outlandish cold opener as a perfect introduction into the zany, darkly comedic, and unapologetically bizarre world of It's Always Sunny in Philadelphia. DeVito's hilarious delivery and quotable lines cement this scene as one of the show's most iconic Frank-related moments.

NEXT: Every Season of 'It's Always Sunny in Philadelphia', Ranked