Guppy Gibson is Gibby's little brother. His first appearance was in iPsycho (although he first makes a cameo in the credits of iSpeed Date as a 5-year old Gibby who likes cheese). Guppy's character is portrayed by the younger brother of Noah Munck in real life, Ethan Munck.
Guppy seems to have similar tendencies to his brother; he frequently takes his shirt off and occasionally gets confused. Throughout the episode iPsycho, his main line that he would say to Gibby was "Happy birthday!" (after Carly, Freddie, and Sam sent an SOS message under the guise of being a "happy birthday" message), even though it actually was not his birthday. This became his "catchphrase" in later episodes. When Nora Dershlit fights Gibby, Guppy cheers him on and soon helps the iCarly trio escape from Nora's basement by unlocking the door for them. Guppy looks up to his older brother and sees him as a role model. He often likes to do exactly what Gibby does, such as when Gibby comes out of the tent and stretches, Guppy follows behind also stretching.
He appears in the closing credits of iSam's Mom, sitting with Spencer and eating spaghetti. He returns for a cameo appearance two episodes later, in iSell Penny-Tees, eating a handful of spaghetti that Sam blew her nose into, and appears in the following two episodes.
In iDo where Gibby rides a bike, Guppy is sitting in a wagon attached. When Gibby sees a five dollar bill, Guppy stares at him. He keeps repeating "Happy Birthday" to him, tempting Gibby to ask him if it was his catchphrase. In another point in the episode, he takes a strong interest in a girl that is passing by.
It is hinted that Guppy may have a small crush on Sam. On the iCarly website in a video called "An iNterview with Guppy: Making Sandwiches" Sam asks Guppy who he would want to marry. He then replied with singing to her "You, you, you, my love." On another video called "Interview with Guppy: Colorful Candy" Sam asks him three things he thinks is beautiful. He answered with, "Um, Sam, and flowers, and strawberries, and fruits." Guppy's older brother Gibby also had a crush on Sam for a short while.
He has a cell phone as proved in iDo when he took a picture of a young girl walking by and when he calls his mom.
Guppy returns in iStart a Fanwar, and he is in the scene where he is in their car while Gibby and his grandfather were trying to order soup. He kept saying things such as "French Fries!", "My shorts are too tight!", and "I'm hearing the voices!". He also sang old campfire songs, which annoyed Gibby.
As Spencer has no kid, nor is he dating anyone in iBust a Thief, he brings Guppy to Funky Fester's Gametorium to gain access to the game room. Guppy makes a dramatic "Happy Birthday!" entrance and questions if Spencer thinks of himself as "normal" when Spencer refers to him as "my little sister's weird friend's weirder little brother".
- Guppy has his own phone as shown in iDo.
- It was said that he had eaten Spencer's hair after he had cut it in iGot a Hot Room (but this is probably not true because eating hair is a choking hazard and hair is indigestible).
- "Guppy" may be a nickname like "Gibby" is.
- Spencer did not know Gibby had a younger brother after he came out and saw Guppy shirtless asked, "What did they do to you?!" mistaking him for Gibby.
- iSell Penny-Tees is the only time he appears and has no lines.
- Charlotte Gibson (mother)
- Mr. Gibson
- Orenthal Cornelius Hayes Gibson (brother)
- Sabrina (cousin)
- Grandfather Gibson (paternal grandfather)
- Grandmother Gibson (paternal grandmother)
- ISpeed Date (appears in end credits)
- IBloop (appears in bloopers)
- IPsycho (first full appearance)
- ISell Penny-Tees (minor cameo in the opening web shop scene, referred to as 'Junior')
- IStart a Fanwar
- IBattle Chip (mentioned only)
- IBust a Thief (final appearance)