There were undoubtedly many, many factors that went into the massive success of How I Met Your Mother across its nine seasons, from oftentimes great writing to its premise to just a slew of excellent episodes and stories. One of the show's best aspects is the characters, with Barney Stinson being one of the most iconic sitcom characters of the past twenty years.
There is no doubt that objectively Barney is a pretty awful person on a multitude of occasions throughout the show, but fans cannot help but love him, with the character going through many changes as the show goes on while still retaining a lot of what makes Barney, Barney.
Changed - P.L.E.A.S.E
There are many running jokes throughout the nine seasons of the show, with one of the biggest being the mystery of Barney's job, the job that provides him with his lavish lifestyle, and a job that, when asked about, he simply replies, "please."
It turns out that Barney was describing his job all along, Provide Legal Exculpation And Sign Everything. Barney revealing his job was not the only big change though, it gets revealed that Barney was working for the feds to get revenge on his boss, Greg, for stealing his girlfriend, obviously quitting his job, likely getting income through his best selling book and other ventures, although this is unconfirmed.
Same - Suits
From the moment we meet Barney, he is in a suit, and very rarely does he ever leave his beloved suits behind for more casual-wear, with one of his most famous catchphrases being "suit-up."
That love of suits never wavers, when he holds his child, agrees to get divorced, announces to the gang their divorce, gets the feds in on his boss, nearly every future event that happens to Barney, he is clad in the finest suits.
Changed - Met His Father
The subject of Barney's upbringing is brought up regularly in the show, often viewed as the source of so many of Barney's insecurities and general issues in his adult life, growing up with an incredible amount of lies from his mother and no father around.
However, Barney eventually finds his father, a figure he is immediately disappointed by, ing him to be so much cooler than he actually is. Nevertheless, Barney's father and the attempt at a relationship they make was a huge change in Barney's life and lifted a weight off his shoulders.
Same - The Fortress Of Barnitude
How I Met Your Mother's central apartment is that of which Ted and Marshall move into after college, which eventually is the residence of every member of the gang at some point, except for Barney.
Barney has his own apartment throughout the entire show, which he absolutely adores. It is all fixed up for his womanizing ways, and as far as fans are aware, it is where he lives in the future when he is not traveling with Robin and past their divorce. Although, after his child's birth, it is likely the Fortress of Barnitude was altered to be more fitting for a child.
Changed - Marriage & The Idea Of Love
Barney is immediately established as a serial womanizer whose opinion on relationships, marriage, and love is as low as his opinions on off-the-rack suits.
However, as the show goes on, he begins to open up more to the possibilities of love. Meeting the likes of Nora and Quinn open up Barney's eyes to how relationships can be, but it is Robin who truly makes Barney want to love, falling for her early, and holding that flame for years until they marry - then divorce with Barney going back to a sleazebag, but there is still a journey and many changes there.
Same - General Personality
Barney obviously changes throughout the show massively in various ways; however, in of Barney's core personality, he remains very similar to his initial self.
Having a child and falling in love changes him. Still, his love of elaborate schemes, deception, sense of humor, love of suits can be extremely childish, a bit dimwitted when it comes to pop culture and geography, and keeps his overall charm and charisma, as well as other key traits of his.
Changed - Opened Up
At the start of the show, Barney was not a hugely complicated character on the surface but obviously had some issues that were thankfully explored as the show went on.
Despite his love of lying, Barney opened up multiple times throughout the show. Despite his insecurities, Barney has talked about his opinions on not having a father multiple times, on his love for Robin, his care for Ted, etc. even about the heartbreak he has experienced and the way he has treated women. Very early, Barney does not come across as the open up type, but alas, despite his flaws, Barney does so throughout the show.
Same - Real Care For His Family & Friends
Right from day one, Barney was a key part of the gang; despite not knowing any of the other three for as long as they knew each other, he was ingrained in their lives, something that stayed true for, as far as we know, the rest of them.
He has an unbelievable love for his friends. While he makes some mistakes with his friends and puts on a front like he does not care, he truly does and shows it time and time again, never looking for praise for his love for them.
Changed - Personal Growth
As mentioned earlier, Barney's personality in of various likes and dislikes and generally what makes him who he is, stayed largely the same throughout the duration of the show, but even still, Barney underwent a lot of personal growth.
Not only did Barney recognize a lot of the issues he had, but he faced a lot of them face on, and on top of that, he appeared to learn from every serious relationship he had. A lot will argue he lost a lot of his development during the finale, and that is fair, but overall he still grew an immense amount as a person.
Changed - Having A Child & Finally Stopping The Playboy Lifestyle
Perhaps the most significant way Barney's development got hindered in the finale was by having him revert to the playboy lifestyle after his divorce from Robin, acting like he did way before he knew how love felt.
That, though, gave way to one of the only redeeming factors of the finale, Barney having a child and finally wanting to settle down, to grow up and give up that life for good.