Whenever Filburt feels uncomfortable or disturbed he is known to say, "I'm nauseous! I'm nauseous!". He also occasionally says, "Oh boy" and "Oh fishsticks." He also popularized the phrase "Turn the page, wash your hands."
Filburt becomes age 21 in the episode "Born to Spawn."
Joe Murray, the creator of the show, originally intended for Filburt to be a secondary character used to "add texture" to Rocko and Heffer Wolfe. Lawrence, also functioning as a director on the show, sculpted Filburt into a main character befriending Rocko and Heffer.
Murray auditioned Lawrence in a large casting call in Los Angeles and chose him as the voice actor for Filburt. Murray stated that he did not expect for Lawrence's "east coast nasal to be so perfect for Filburt."
Martin Olson, a writer, described the decision when Nickelodeon gave the "okay" for the marriage of Filburt and Paula Hutchinson as one of the most memorable moments of the production. Olson said that the executives at first did not like the idea; linear character development did not exist in Nicktoons. Murray convinced the executives to allow for the marriage to occur.
Filburt, described on the Australian website as "nerdy" and "neurotic," bears many phobias. Filburt, a former "genius," "babe magnet," and "star athlete," became ruined by a case of "unrequited love." The Nickelodeon South East Asia website states "think of Woody Allen when you think of Filburt."
His birth place is Kerplop-it-goes Island (named after the Galápagos Islands); on his 21st birthday, as dictated by nature, he is required to go back to the island for a period of time.
Filburt and Dr. Paula Hutchison have four children, Gilbert, Shellbert, Norbert, and Missy who all came from the same egg. Gilbert and Shellbert look exactly like Filburt while Missy is a miniature version of Hutchison. Norbert, on the other hand, has Filburt's eyes but oddly resembles Heffer, who took on the job of "egg-sitting" (literally, sitting on the egg to keep it warm) for Filburt when they realized Filburt's rear was too hard for the task. Norbert also often thinks that Rocko is his father. Filburt actually holds the record number of jobs on the series: nine. These include a cashier at a grocery store (Rocko's Happy Sack), cashier at Kind-of-A-Lot-O-Comics (Power Trip), license checker at the Department O' Motor Vehicles (Skid Marks), film runner at the GooglePlex Cinemas (Popcorn Pandemonium), lounge singer (The Lounge Singer), Christmas tree salesman (Rocko's Modern Christmas), photographer (Hair Licked), cook at Stuff on a Stick (Pranksters), and a food sample carrier (Put out to Pasture). In one episode, it is shown that when between jobs, Filburt apparently supports himself by recycling an enormous collection of empty cans in his trailer at the Patch-O-Heaven Trailer Park; this prompted Rocko to comment, "So this is why he never works." According to geneal records of him, he is 44% Dutch, 43% French, and 13% German.
In the comic book Filbert does not meet Hutch; instead in the first story in Issue#7 he meets a female turtle named Cindy at a comic book convention.
A running gag in the series is how multiple, mundane things give Filbert nausea. This is always followed with Filbert repetitivly saying, "I'm nauseous, I'm nauseous, I'm nauseous...". At the end of the episode "Sailing the Seven Zzz's", while in a sub, we hear Filbert about to say it, only to hear Rocko and Heffer say "You're nauseous", at which point he says "Right" and vomits.