"[1] Salling gained 20 pounds (9.1 kg) before filming the pilot episode in order to better embody his football playing character.

He has sexual encounters with his female pool-cleaning clients and fellow students, including a recurrent relationship with cheerleader Santana Lopez (Naya Rivera) that seems to be casual, though Santana confronts both Mercedes Jones (Amber Riley) and Lauren Zizes (Ashley Fink) when Puck starts pursuing them in the first and second seasons respectively.

He falls in love with Quinn Fabray (Dianna Agron) after he takes her virginity and impregnates her despite the fact that she's dating his best friend Finn Hudson (Cory Monteith) at the time, but he can't give up flirting with and seducing others even when Quinn contemplates raising the baby-to-be with him as he wants rather than giving it up for adoption, since she refuses to have sex with him again.

The brief pairing of Puck with Rachel Berry (Lea Michele) in the episode "Mash-Up", spurred by his mother urging him to find a Jewish girlfriend, dissolves because he wants Quinn and she wants Finn.

Within a couple of months, he has fallen in love with her, but she doesn't succumb to his blandishments, and he's forced to woo her over a long period of time, starting as friends.

Puck is introduced as a football player and bully at William McKinley High School; he is frequently seen throwing fellow students into dumpsters, or tossing slushies in their faces.

He is the best friend of Finn, the quarterback,[6] and has a summer pool-cleaning business that leads to sexual encounters with his adult female clients.

Despite that, he has sex with fellow students, including in an on-again, off-again relationship with Santana Lopez, a cheerleader, which does not completely end forever until the middle of the second season.

[7] Puck initially acts homophobic and mocks Finn for joining the school glee club, New Directions, but later becomes a part of glee club director Will Schuester's (Matthew Morrison) all-male a cappella group, the Acafellas, hoping to impress the mothers at a performance for the school's PTA meeting.

He offers financials to Quinn to show he will be a good father and provider; she figures out that it's the money from the bake sale, and refuses to accept it, though she expresses her gratitude and apologizes for her previous insult.

[9] Quinn reconsiders her plan to have the baby adopted and gives Puck a chance to prove himself by helping her to babysit Terri Schuester's (Jessalyn Gilsig) three nephews.

Beth is adopted by Rachel's birth mother Shelby Corcoran (Idina Menzel), the coach of Vocal Adrenaline, the show choir that defeated New Directions at Regionals.

In the season opener, "Audition", Puck is interviewed by blogger Jacob Ben Israel (Josh Sussman) and reveals that he had a vasectomy over the summer, saying it was the only responsible thing to do.

In "Furt", Puck, Artie, Mike Chang (Harry Shum Jr.) and Sam Evans (Chord Overstreet) confront Dave Karofsky (Max Adler) in the boys locker room to get him to stop bullying Kurt Hummel (Chris Colfer).

Because he was still on probation, Puck reluctantly had to watch the beat down between Sam and Karofsky, but despite not being allowed to fight and feeling helpless about it, he showed great restraint and was still praised for standing up for Kurt.

"Special Education", Puck is asked by Will to find a new glee club member to replace Kurt, who has left McKinley and New Directions.

He tries to recruit from the football team, but they lock him in a port-a-potty; he is rescued the next day by Lauren Zizes (Ashley Fink), who becomes the club's new twelfth member.

Puck and Finn finally settle their differences in "The Sue Sylvester Shuffle", and they work together to help the football team win its first-ever championship.

[12] Neither Puck nor Lauren win the race for prom queen and king,[13] but they remain a couple; they fly with the rest of New Directions to the nationals competition in New York City, where the glee club comes in twelfth out of fifty teams.

[14] Lauren breaks up with Puck at the beginning of school year and drops out of glee club, claiming that it is hurting her reputation.

Coach Beiste (Dot-Marie Jones) breaks up the fight and she informs Puck that he could get expelled from school for bringing the knife.

Puck decides to return to Lima to live, and the two Puckermans arrange for their mothers to meet on Christmas Day where the two families bond.

Puck sings Avril Lavigne's song Keep Holding On to her hoping that this would win her heart, but she turns him down stating that she loves Biff.

Puck leaves the locker room heartbroken and storms down the hallway when Quinn runs after him and kisses him, agreeing to give their relationship another chance.

"[21] Raymund Flandez of The Wall Street Journal described Puck's voice on the song as "earthly, sensual and full", and Entertainment Weekly's Michael Slezak said that Salling did "more than a serviceable job".

Flandez said of Puck in the first-season episode "Mash-Up" that we finally saw him "emerging from his bonehead-punk exterior", and that he "wows us with his sensitive, cool guy turn as a solo singer" performing “Sweet Caroline”.

Club wrote, "Mark Salling just seems to have a ridiculous amount of chemistry with all of the female cast members in the show, and it's fun to see him and Dianna Agron get in that food fight.

Robert Canning of IGN said the "absolute best part" of the "Silly Love Songs" episode was Puck's "unexpected longing for Lauren Zizes.

Fink ends up being a good match for him, chemistry-wise, as she projects a confidence and certainty that makes it immediately obvious just what Puck sees in Lauren.

"[27] In the following episode, VanDerWerff found her relationship with Puck "a lot less assured" than before,[28] but Entertainment Weekly's Sandra Gonzalez deemed their scenes "as endearing as they are unrealistic",[29] and E!