Gunther has a smoking habit in common with Chandler. Since season 3, he has had a consistent unrequited love for Rachel but only gets the courage to confess in the series finale, when he finds out that she is going to Paris. Gunther used to be an actor, having played a character called Bryce in All My Children. Being killed off by getting buried in an avalanche is how he ends up being a waiter at Central Perk. He confesses this to Joey in "The One Where Eddie Won't Go", after Joey confides in him that his character, Dr. Drake Ramoray, was thrown down a shaft in daytime show Days of our Lives.
Though Gunther is a permanent fixture in the everyday lives of the friends, he never penetrates the inner circle. This becomes a running joke. At Ross' bachelor party, Chandler announces Gunther as his best man, to which Gunther instantly replies: "What's my last name?". Chandler defeatedly answers "Central Perk?". Another example of this is when Ross is celebrating getting tenure. Ross asks Gunther for six glasses, to which Gunther asks hopefully "You want me to join you?". Ross replies "Oh, I thought Joey was here - five is good."
Gunther is on good enough terms with the friends, however, to often be invited to their informal parties, such as Phoebe's birthday party, Rachel's birthday party, Emily's farewell party, Ross' bachelor party, Rachel's premature surprise birthday party and Chandler and Monica's Halloween party. He is, however, left out of the official formalities, like Ross' London wedding and Monica and Chandler's wedding, but he attends Phoebe's wedding.
In a 2019 interview, James Michael Tyler said he thought Gunther would be the owner of Central Perk and a very small apartment in either the East or West Village, but is content with his life.
Gunther's peroxide blonde hair is a source of much entertainment. Rachel describes it as being "as bright as the sun," and when Gunther tells Joey he has an appointment to have it dyed, Joey says: "But I love your natural color." When guessing the identity of the father of Rachel's baby, Phoebe asks: "Is it Gunther?" Rachel denies this, to which Phoebe says: "Thank God, because that hair on a baby?"
Gunther is commonly used as an unattractive alternative to the main friends, but confusingly, is sometimes seen as somewhat of a sex symbol towards the end of the show. In Season 5, when helping Rachel get over Ross, Monica includes Gunther in the list of prospective dates for Rachel, which he overhears and shows off his posture in reply. Rachel begins to say "I guess he is kind of cute" only to be thrown off course by an old flirt of hers, which Gunther identifies and throws out of Central Perk. Ross and Monica's mother, Judy, remarks how Gunther is a "sexy blond" and prominently adds him to her "list" of people she can sleep with without cheating.
Phoebe also gives small impressions that she may secretly be attracted to Gunther, despite often mocking him before ("That hair on a baby!"). She once remarked "Sure, Gunther is sexy in an obvious way...", and when referring to the number of attractive men in Paris, says that "it's like a city of Gunthers". She also does not hesitate at all to kiss Gunther in "The One With Joey's New Girlfriend", although her main objective is that of catching a cold, and she does not kiss him until she hears him sneeze.
In Season 3 it emerged that Gunther had a crush on Rachel. He often fantasized about marrying her and let it slip to Joey that one of the perks of his job was being able to stare at her all day. He was jealous of any other men who got into a relationship with her, including Ross and at Ross' bachelor party before his marriage to Emily Waltham he thanks him for not marrying Rachel and on a different night, he whispers to Emily that "Rachel is my girlfriend".
Gunther would give Rachel anything she wants. This is shown, for instance, in "The One With The Joke", Rachel was angry with Gunther for firing Joey after Joey left work to go to an audition, even though Joey was new and shouldn't have been left in charge. She then demanded that Gunther give Joey his job back, which he immediately agreed to, without question, showing that all Rachel has to do to get something from Gunther is ask for it.
When Rachel wants to have a relationship like Emily and Ross', she proposes to Joshua, but he refuses. Gunther comes up to him and screams "YOU IDIOT!". When Phoebe kisses him to get her cold back, he apologizes to Rachel for not stopping the kiss. Ironically, Rachel mistakenly assumed that Gunther is gay, arriving to the point that in one episode. In what she thought was an encouraging remark, she tells him one day he would make "some guy the luckiest man in the world". In "The One With All The Kissing", Dave, who agrees to go on a date with Rachel, is refused service at Central Perk by Gunther for that very reason.
Also, when Rachel buys a sphinx cat and decides she has to sell it, the only person who wants to buy it is Gunther, and Rachel even gets a profit on it. The only reason he buys it is so Rachel will come visit it but that doesn't work out.
Gunther disliked Ross for being Rachel's boyfriend, once bitterly telling him in response to Ross making an order in the coffee shop "Oh, like you don't already have everything." His dislike for Ross deepened when the latter became the father of her daughter. Overcome with bitter jealousy, Gunther bans Ross from hanging flyers in the coffee house despite allowing everyone else to do it and looks amused when he at one point sees Ross hurt his hand. He also, with little, if any, regard for her feelings, didn't hesitate to tell Rachel when he learned that Ross, mistakenly thinking at the time that his relationship with her was over, had drunkenly had sex with another woman. He also seemed to take satisfaction in rubbing the fact that he had revealed the drunken romp to Rachel in Ross' face, as when Ross found out that he knew about it and begged him not to tell her, Gunther mockingly replied "Was I not supposed to?"
In Season 8, when Gunther overhears Joey telling Ross about his newfound love for Rachel, after Ross has left he sneaks up behind Joey and, just like Ross did, screams "Rachel?!". In the series finale, he confesses his love for Rachel and she realizes he wasn't gay. Though flattered, she tells him she loves him too but not in the same way and then tells him she'll think of him whenever she's in a café having coffee or when she sees someone "with hair brighter than the sun" and gives him a kiss on the cheek before leaving. It's hinted that Ross and Rachel get married to each other again after the series finale, which would likely increase his jealousy of Ross. Although shocked when Gunther revealed his feelings to Rachel, it's unknown if this resulted in Ross becoming jealous of Gunther.
In the board game Friends: Scene It?, Gunther is also the narrator. During the Final Cut turns and sometimes the end, when the winner is congratulated, Gunther will tell the player(s) what to do or congratulate the winner. Before leaving, he says, "Rachel is my girlfriend."
- Gunther is fluent in Dutch, once calling Ross an 'ezel' (literally: donkey). Ross looks up the word 'ezel' in the dictionary and retorts to Gunther "You're an 'ezel!'". Gunther easily overrules Ross by saying "Jij hebt seks met ezels" (literally: "You have sex with donkeys"), leaving Ross baffled, not knowing what the sentence meant.
- Tyler had his hair dyed the day before his audition - one of the actor's friends, who had studied to become a hairdresser, experimented on his hair. When Tyler showed up, the producer liked it so much that they decided to keep it.
- Gunther didn't have a line until the 33rd episode he was in, in which he only had one word to say: "Yeah".
- He's the character with most appearances after the main cast, with 185 episodes, though the majority of these are non-speaking and uncredited as he is simply behind the bar during scenes with the main cast interacting in the coffeehouse.
- One idea considered by the writers was for Rachel to move in with him. However, this was dropped after protests by James Michael Tyler and Jennifer Aniston.
- Gunther was once kissed by Phoebe but no mention of it is made later in the series.
- In part Gunther fulfills the role intended for Terry, the owner of the coffeehouse.