- Edgar (and Ellen)'s last name hasn't been revealed yet, although it is believed to be "Schadenfreude" due to the sign on the Tower Mansion's front door.
- Before the Tower Mansion was destroyed, Edgar liked to play the funeral march in an old pipe organ and played by ear.
- He gathers strange objects in his satchel, and keeps them for disastrous inventive uses.
- When he was younger Edgar used to sing a lullaby to Pet. ("Tourist Trap")
- Edgar can cook gruel and porridge. ("Split Ends")
- Edgar is more violent with his sister in the book than he is in the show, pulling her around by her hair, tackling and.kicking her. ("Frost Bites")
- He has a scar on one of his thumbs from Berenice biting him with one of her tooth-like seeds.
- It has been hinted that Edgar might have a crush on Imogen. ("Split Ends")
- Edgar got trapped under a kiddie pool as a young child, making him deathly afraid of pools since then. ("Off the Deep End")
- Edgar's experimentation in the lab appears to be more profound than it is in the books, seeing as he successfully makes transformation potions and growth serums. ("Gross Inspection")("Trick or Twins")
- While it is understood that Edgar's satchel is 'bottomless', he pulls much larger and ridiculous things out of it in the TV series, such as a giant fan, a port-o-potty and (unsuccessfully) a leprechaun.
- Edgar uses physical representations in his planning (such as dioramas and figurines), and gets very defensive about them when Ellen insists they’re his ‘dolls’ and ‘dollhouse’. ("Ellen vs. Slug")("The Secret Life of Pet: Hard-Boiled Pet")
- He acts more like a typical twelve-year-old boy, enjoying things like collecting (mad scientist) trading cards and monster trucks (The 'Ed-GRR'). ("Prankster Wannabe")("Nuggets of Stupidity")
- Edgar is right handed while Ellen is left handed.