|“Poor boy! You can't beat us, so why don't you join us?!”|
|— Lady Evelina to Jack, "Grave Situation"|
The Boss Ghosts are the main adversaries of LEGO Hidden Side.
- Many of the Boss Ghosts are Humans, though a few come in the form of strange spiritual forms of inanimate objects, items, or odd creatures, such as Spewer or The Maw.
- Mr. Nibs is a Human, but he took on the appearance of Lady E's old Teddy Bear.
- The Boss Ghosts that appeared in the largest LEGO Hidden Side set of each wave are usually viewed as the final boss of the wave.
- All of the Boss Ghosts have an important item that's tied to them, which can then be used in summoning them.
- Trucker Dale, Tragico, Blaze M. Barr, and Maxine Turbo are the only Boss Ghosts with a known death.
- Lady E., Mamali, Anomalo, and The Bawa are the only Boss Ghosts that don't resemble a big-fig.
- All of the Final Boss Ghosts except Tragico are Sad Ghosts.
- Samuel Mason (highwayman), Trucker Dale (Car thief), Joe Ishmael (Looting sunken ships), Kreatoru (Joe’s partner-in-crime), Rat Shaun (bank robber), and Blaze M. Barr (Arson), are the only known boss ghosts who were known for a certain crime in life.
- Most of the Boss Ghosts had some connection to Lady Evelina in life, but others, such as Trucker Dale, only became associated with her after their death.
- The only boss Wave 1 and 2 boss ghost to survive the events of Seasons 1 and 2 is Mr. Nibs.
- All three waves have at least one Boss Ghost associated with water: