It is massively questioned whether Plank really is alive or not due to the various implications of Plank moving, such as the scene in "Gimme, Gimme Never Ed." In the episode, Eddy seems to dislike him for hurting him in various ways. Plank is somehow enrolled in Peach Creek Jr. High and plays on the football team. In "Too Smart for His Own Ed," he participates in the annual school spelling bee (although he gets kicked out in the first round because nobody besides Jonny hears him speak).
Plank is almost always seen with Jonny. The two are near-inseparable and do everything together. For example, when Jonny became Captain Melonhead in the episode "Robbin' Ed," Plank became Splinter the Wonderwood, Jonny's sidekick. Plank is implied by Jonny to be a bit of a prankster and a wiseguy, and is often blamed for causing his troublesome predicaments. Jonny is so engrossed in the world of his best friend that he even created parents and friends for Plank out of other pieces of wood laying around.
Plank is confirmed by Danny Antonucci to be nothing more than an inanimate block of wood in the Season 2 Compilation. Plank has been Jonny's best friend since he was a toddler. Plank speaks and expresses himself through Jonny, with Jonny saying "Plank says..." whenever Plank wants to say something to someone other than Jonny, and moves around by having Jonny carry him around (however, in the episode "All Eds Are Off," he is seen moving throughout the school campus without Jonny's assistance). Despite being an inanimate object he seems to have a personality and mind. There are several instances where Plank shown signs of a having his own mind and personality. For example, in the episode "Gimme, Gimme Never Ed," Jonny reveals he receives an allowance and manipulates the Eds to ride their death-defying (and poorly constructed) ride, Requiem for a Whiplash for five dollars, despite Jonny's warning that Plank is just looking for kicks. Another instance of him showing signs of having a mind is in the episode "Dear Ed," where Jonny and Plank break their friendship due to an unseen argument which happened before the episode started. In the episode "Tinker Ed," he is seen reading the book, Mind Control for Pre-Pubescents in the school library as Jonny sits beside him, looking like a mindless dolt. He is generally accepted as a living being by the kids and the Eds (save for Eddy, who dismisses him as a piece of lumber). The Kankers, on the other hand, see him as a backscratcher and have used him as such on a few occasions. Plank is usually seen hanging out with the kids (only if Jonny is present) and is often, if not always, seen nearby or with Jonny.
Plank also seems to have some control over Jonny; in "All Eds Are Off," Jonny had a hard time making decisions and found that he couldn't do much without him, and failed to last a day separated from him. Another instance when he reads Mind Control for Pre-Pubescents (previously stated above), indicating that he knows how to control Jonny. This may have been written in by the animators as a humorous gag or to add more mystery to Jonny and Plank's relationship, however. Jonny is very protective of Plank and is willing to pick a fight with anyone who threatens to harm him. He is very moody when he is separated from Plank, as seen in the episodes "Home Cooked Eds," "All Eds Are Off," "Urban Ed," and "Dear Ed."
Plank is stated to be a male, as most of the kids refer to Plank as "he" (if they're not referring him as a piece of wood) and is seen taking gym class with the boys.
Plank is a yellow piece of wood with a blue curved line for his mouth, red circles for eyes, and blue dots for pupils. He also has a chip in the upper right corner of his head, which is further explored in "Every Which Way But Ed".
Old Plank, seen in "Take This Ed and Shove It", seems to have rotted over the years. Half of his mouth seems to have been rubbed off with the passage of time (similar to his mouth being wiped off in "If It Smells Like an Ed") and he has been bleached white. Not only has half his mouth been smudged, his left eye seems to have suffered the same fate. While still old, Plank and Jonny have remained together as best friends after 90 years. He now plays chess with Jonny a lot and appears to now help Jonny see things since Jonny is blind in one eye.
Plank's Parents appeared in "Postcards from the Ed." They appear to be very hyper tourists. They carried cameras and wore Hawaiian T-shirts among other notable tourist garb. Eddy tries to give them a tour around the Cul-de-Sac, but they end up losing their heads on the monkey bars in the playground due to his recklessness (and being made of wood, their inability to duck), much to Jonny's shock. In the end, the Eds are shown up in a tree surrounded by wooden pirates and thugs, possibly either family members, friends, or close connections to Plank, as Jonny warns the Eds that Plank knows people.
Splinter the Wonderwood
Splinter the Wonderwood is Plank's superhero alter-ego, and Captain Melonhead's sidekick. Splinter can become a transportation vehicle for Melonhead and is also used to help Melonhead fight. He is a weakness for the Captain, though; if his sidekick is captured and threatened, Melonhead gives up as he doesn't want anything to happen to his fellow friend. A prime example is in "Robbin' Ed", when Eddy (Professor Scam) threatens to spray Splinter with water if Melonhead gets any closer. Water is Splinter's only weakness (he's wood, after all). He only appears in the episode "Robbin' Ed" and in Ed, Edd n Eddy's Big Picture Show, alongside Captain Melonhead.
Timber the Dark Shard
Timber the Dark Shard is Plank's supervillain alter-ego, which is The Gourd's evil cohort. It is possible he retains all abilities from when he was Splinter (i.e. mode of transportation), and is probably still weak against water.
He appears in the epilogue of the movie, where Captain Melonhead and Splinter the Wonderwood escape, badly beaten, and become The Gourd and Timber the Dark Shard in order to get revenge on the Eds and their new friends. However, their schemes are curtailed when Timber reminds the Gourd that the movie is over. The Gourd is surprised by this; apparently he didn't even know they were in a movie.
- There are thirteen different characters that are imaginary friends in the show besides Plank: Bob, Salty Sam, Sawtooth Cecil, Plank's mother, Plank's father, and seven wooden toughs Plank knows somehow.
- In the game FusionFall, while Plank isn't in the game, there are two giant replicas of Plank guarding the Fort and serving as its entrance. You also have to make a Fusion Plank so you can enter Fusion Edd's secret lair for the second battle against him.
- Ed seems to (at times) see Plank as a genuine living being, making him the only person besides Jonny to do so. However, this is most likely due to Ed's overactive imagination, as in "Gimme, Gimme Never Ed," he claims that Plank shouldn't speak, as he wouldn't hear him anyway.
- He is a member of the Urban Rangers, along with Rolf, Jonny, and Jimmy.
- On his ID in the Invaded special, it says he is an Expert in Chinese Literature. This may be a reference to "For Your Ed Only" where Jonny and Plank end up going so far into Earth, they come out in China.
- It is known that Plank (and Jonny) hates broccoli as revealed in "Will Work for Ed."
- In an episode of Two and a Half Men ("The Price of Healthy Gums Is Eternal Vigilance"), a Plank plush toy can be seen on Jake's bed.
- Apparently Jonny was somehow able to be tutored by Plank as stated in the episode "Mission Ed-Possible."
- Goof: Plank is vulnerable to water and swells up when he comes in contact with it, but in "Quick Shot Ed" he is seen having a bath with Jonny.
- The creators originally intended for Plank to be sentient. Danny Antonucci, however, responded with "It's just a piece of wood."
- Plank also has a character sheet to model his different "expressions."
- Jonny 2x4
- My Best Friend Plank
- Urban Rangers
- Plank Family Players
- Plank's Parents
- Plank's Groovy Arbor Day Party