Pen is BFDI's coolest character. He's a ballpoint pen with blue ink. When an easy shortcut presents itself, Pen knows how to take it. However, he and Tree sometimes have to ask Black Hole for help. His best friend is Eraser. Blocky is friends with both.

Despite his problem-solving skills, Pen's empty promises put him in a debt worth more than 6,398 quindecillion times the price of the world.

Did You Know?: Pen gets jealous every time he sees Pencil erase something she wrote.

Emotional Isolation: Despite having friends, in TPOT's run, he has been losing many friends due to elimination, which causes Pen to have insecurities about it.

Strategization: Despite being dimwitted at times, Pen can be pretty good at strategizing, such as tricking Four into screeching his team inside them, tricking Black Hole to stop him from sucking his other team's blocks and using Golf Ball's Shrink-A-Tron to get the Dream Berry.
Blowing wind far: Pen won 1st place for Death P.A.C.T. in "Getting Teardrop to Talk" after blowing X's basket toward him from a really far distance.
Strength: In "What's Up Bell's String?", Pen is strong enough to lift a tree off the ground and hit Needle with it. In "The Power of Four", he is shown to be able to flip over the FreeSmart SuperVan.

Speed: While Pen is not as fast as Needle or Firey, he shows himself to be somewhat fast, as shown in the ladder climbing challenge when Pen was able to win 1st place. He's also able to briefly run faster than Needle in "What's Up Bell's String?".
Drawing: Being a pen, Pen can use his pen point to draw.
Climbing: Pen is able to get 1st place in "A Leg Up in the Race" and is also shown quickly climbing a tower of blocks in "The Worst Day of Black Hole's Life".

Pen is a kind, empathetic, and loyal character, contrasting with his more aggressive or indifferent peers. He shows his caring nature by helping Rubber Spatula feel better about being the least voted to join and encourages a positive outlook. During “The Power of Four” Pen offers to listen to Liy talk about how she felt about her time in the E.X.I.T. after she mentioned her distaste of waterfalls.

Pen has also shown to be competitive and playful but can act impulsively, like during his rivalry with Needle in "What's Up Bell's String?", which later turns into a friendship he values deeply. He struggles with the eliminations of Needle and Eraser in "Category One" and "I SAID CAREFUL!!!" respectively, becoming increasingly paranoid about losing more. Despite this, Pen is still sympathetic, even to those who hurt him, like Pencil, whom he helps after understanding her fear of Four.

"Bottle For Dream Island" further cements Pen's attachment-based abandonment issues as he struggles to cope with the loss of his two close friends and tries to re-kindle a now-distant friendship with another member his old friend group, Snowball. Still, he is shown to be a very empathic person by trying to console Pencil about her emotions, sympathizing with her after noticing that she was struggling to maintain friendships as well. He’s actively growing more and more as a person with the help of Liy’s guidance.

Pen appears to be a lot more competitive, outgoing and hard-working, and he is a lot more active within his team. A large portion of Pen's screen time in BFB was competing in challenges. His greater participation in challenges may be due to his lack of interaction with the other former "cool" characters, as they were separated when the teams were being formed.

Pen has also shown himself to be a bit naive. He also didn't realize that Tree being stuck inside Bottle would give their team a disadvantage in "This Episode Is About Basketball". Pen proceeds to yell at Tree for not being able to toss the balls well. When Pie brings up the fact that there may be another solution, Pen throws the balls into Black Hole, in hopes of getting them into the basket. Pen also shows a sense of duty and honor in his role on Death P.A.C.T. Despite wanting to help Blocky with his deadly pranks, Pen chooses to keep preventing death so as to not betray his team's trust.

Despite not competing, Pen shows a timid side in the Tiny Loser Chamber, such as in "Well, Look Who It Is!", where he is horrified of Pin's glitching and Gelatin's laser shot.

Pen is generally kinder and more considerate than his friends, which makes him stand out for his politeness and gratitude. An example of this is in "Return of the Hang Glider", when Firey allows Pen and his three friends into Dream Island, Pen is the only one who thanks him. A more subtle example is whenever the eliminated contestants voted for anyone but Leafy to win Dream Island, Pen is the only one out of his friends who didn't slap them for it. Pen has also shown himself to be a bit dimwitted, however. One example of this can be seen in "Sweet Tooth" when he thought 8 dollars could buy two 5 dollar cakes.

He is a generic capped ballpoint pen. His body is slim and white, and his cap is a light blue color. Despite his blue cap, Pen's ink appears to be black or indigo. In early BFDI, his rear shading and bottom were curved, but later on they became straight.