His first appearance was in "Overnight Success", as one of the kids Lincoln invited to his sleepover, after Lincoln had a falling out with Clyde. Since then, he has made other appearances in other episodes.
Personality
So far, not much known is about him, other than that he is one of Lincoln's best friends. He likes basketball and rock music. He seems to be from the countryside given his accent and during "Back Out There" where he mentions doing stereotypical agricultural activities such as milking cows and that donkey poo was hard to get out. He also doesn't seem to be able to understand certain metaphorical phrases, such as Rocky's dad complimenting them on their appearance and telling them they'd need to fight the ladies off with a stick, causing him to sadly remark that he had forgotten his stick.
Appearance
Liam in his basketball outfit.
Liam is as tall as Lincoln and has freckles on his cheeks. He has orange hair styled into a bowl cut, and two buck teeth.
His regular clothing attire consists of a light and dark green striped t-shirt, brown shorts, white sneakers with green stripes, and white socks with red and blue stripes.
In some occasions, he wears a red basketball outfit.
Trivia
He speaks in a Southern accent.
He is the only member in Lincoln's friend group that hasn't had their last name revealed.
He was the only person whom Lincoln's advice about girls works for in "Lincoln Loud: Girl Guru".
Liam with his unnamed girlfriend, who was never seen again.
Despite getting a girlfriend in "Lincoln Loud: Girl Guru", in "Dance, Dance Resolution", he is dateless. It is possible that his girlfriend broke up with him prior to "Dance, Dance Resolution", the series' continuity is not consistent, or the episodes were aired out of production order.
How his buck teeth are lined up can vary. Sometimes they're lined up right next to each-other, sometimes there's a gap in between them.
He's revealed to have a younger sister in "Making the Grade", who's in kindergarten.
So far, Liam, Ronnie Anne and Rusty are Lincoln's only known schoolmates who have siblings.
He claims in "Out of the Picture", that a kid from the school who was forgotten, lives behind his barn, though it is unknown if this is true or if he made it up.
In the same episode, he can be seen in the group photo of the Chess Club, which implies he is a member of this club.
Liam breaks the fourth wall in "Pasture Bedtime", when he tells the viewers to never cross him again.
He also breaks the fourth wall in Back Out There. After he said "Who's up for a boy's day out music montage?", a second later, a montage of the boys hanging out starts.
Liam, along with Rusty and Zach, are the first recurring characters to get an episode centered entirely around them.
In "Antiqued Off", it is revealed that the magic trick where they take coins out of your ear makes him angry.
"Family Bonding" reveals that yogurt doesn't agree with him.
