He is a yellow-colored lightbulb man with a few hairs sticking out of his bald head. He wears a light blue shirt, along with a red tie. He also wears white underwear instead of wearing pants. He has a black mustache, and a black mole, as well.
He is very friendly, and willing to help out complete strangers without too many qualms, as showcased in both "The Awkwardness" and "The Cycle." He also seems to be very patient, not minding the abuse he endures due to Gumball's and Hot Dog Guy's antics, along with Harold's cruelty. However, "The Ghouls" shows that he is also perverted and creepy, as he spies on children trick-or-treating while sitting in a tree.
- "The Awkwardness": He makes three appearances: the first time is on the city bus, the second time is in the bathroom, and the third time is outside the mall, where Gumball tosses him in the trash.
- "The Console": He can be seen at the park.
- "The Cycle": He becomes Harold's butler.
- "The Ex": He tells Gumball he does not mind cutting his brakes.
- "The Uncle": He appears on the plane.
- "The Worst": His picture appears on the Employee of the Month board.
- "The Deal": He is seen at the Rainbow Factory.
- "The Line": He is one of the people in line for Stellar Odyssey.
- "The List": He is on the plane on Elmore Maps.
- "The Sucker": He is shown presenting the cake to Julius' parents.
- "The Cringe": He appears in a flashback.
- "The Neighbor": He is kicked out of the mall's elevator by Gary.
- "The Anybody": His scooter is taken by Gumball. He later appears watching Stellar Odyssey in the cinema.
- "The Faith": He is part of the crowd at Elmore Stadium, and joins the milk guy and several others in supporting magic over embroidery.
- "The Shippening": He is shipped with the book doctor by Sarah and shatters.
- "The Founder": He works at Chanax.
- "The Schooling": He gets a haircut.
- "The Intelligence": He dunks Mrs. Robinson.
- "The Understanding": He runs out of the bank.
- "The Ghouls": He sings "All Hail All Hallow's Eve!" Later he is carried away by a flying vampire.
- "The Slip": He is in line at Joyful Burger.
- "The Master": He is thrown out of a tavern.
- "The Factory": He works at the Rainbow Factory.
- "The Agent": Gumball throws a wig at him and Bernice.
- "The Web": He accidentally hits himself in the eye.
- "The Heart": He stalks Gumball and Darwin.
- "The Revolt": He is attacked by the objects.
- "The Decisions": He is at the mall.
- One of his early designs resembles his voice actor Mic Graves.
- There is a recurring gag where he runs into Gumball, Gumball ignores him, and the conversation ends with him saying "I don't mind."
- Leonard's name is revealed in "The Deal" during "Employee of the Month."
- He was also revealed to be an Employee of the Month of the Rainbow Factory in the same sequence.
- He is the second character to be named after Daniel Lennard, the first being the Watterson kids' imaginary Daniel Lennard.
- According to "The Shippening," he is shatterable.