The Super Mario series is one of Nintendo's most family-friendly properties. The series officially kicked off in 1985 with Super Mario Bros for the NES, and has slowly evolved into one of the most beloved video game franchises of all time. However, despite the colorful world of the games, it occasionally crosses into unsettling territory.

Whether it's a mainline game or a spin-off, the Mario series has its fair share of creepy moments. Some games, like the Luigi's Mansion or Paper Mario series, lean into the franchise's more odd and uncanny aspects. Nevertheless, these ten moments stand out as some of the most disturbing things to happen in the Mario series.

10 Bowser Jr. Thinks Princess Peach Is His "Mama"

Bowser Junior standing in front of Peach calling her his

Super Mario Sunshine was a significant entry in the series for introducing fans to Bowser Jr, the petulant son of Mario's nemesis. Since then, the character has appeared all over the Mario franchise, even becoming playable in Super Smash Bros. 4. However, his involvement in the story of Sunshine is quite odd.

Disguising himself as Shadow Mario, Bowser Jr. kidnaps Princess Peach, continuously calling her his "mama." Apparently, Bowser has convinced his son that Peach is his mother, which begs many questions about Bowser's parenting decisions. In an ending scene, Bowser admits he lied to his son, who claims he knew the truth anyway.

9 The Never-Ending Staircase

Mario climbing the never-ending staircase backwards

Long-time fans of the Mario series have spent hours searching the beloved Super Mario 64 and finding all its hidden details and Easter eggs. However, some of its most disturbing secrets are hidden in plain sight. That's certainly the case with the endless staircase that players can find.

If players cross the door to the final level before collecting 70 Power Stars, they'll be met with a long staircase. Players can attempt to climb it as long as they can, but they will never reach the end. Not only that, but chilling, looping music plays over this pointless attempt, adding to the sense of dread in reaching the final boss.

8 A Ghost Lurking In The Background

The secret ghost that appears in World 4-4 in Super Mario 3D Land

Super Mario 3D Land for the Nintendo 3DS features the Mario series' classic playful tone. However, the game also consists of the franchise's typical Ghost House levels, placing Mario in spooky mansions haunted by Boos. Eagle-eyed fans will be able to spot this creepy Easter egg.

Once players reach the flagpole at the end of World 4-4, make Mario stand on the fence wall behind it. After waiting a few seconds, a ghostly figure will appear and then slowly fade away. The appearance of this ghost has led to many fan theories about what it is, and if its placement in the game was intentional or not.

7 Getting Way Too Close With Bowser

Mario and Luigi battling enemies inside Bowser's body

The Mario & Luigi series places the video game world's favorite siblings in a turn-based RPG format. The tone of this series differs drastically from the mainline games, often bordering on absurd or nightmarish. One entry in the series, however, forgoes that tone for something a lot more disgusting.

In the story of Mario & Luigi's: Bowser's Inside Story, the plumbing duo are sucked inside Bowser's innards. They spend a majority of the game navigating Bowser's organs and defeating the enemies inside. Along the way, Mario and Luigi also help Bowser deal with several medical issues, which is definitely above their pay-grade.

6 Luigi Fights A Baby

Chauncey with a rocking horse during his boss battle in Luigi's Mansion

Luigi's Mansion is one of the most disturbing games in the Mario series, as it puts Mario's frightened brother Luigi at odds with ghosts that he must catch. In his adventure through the mansion to find Mario, Luigi comes across many boss characters who represent members of the family who once lived in that house.

One of the earliest boss characters is Chauncey, a ghost baby. Fans of Luigi's Mansion are probably very familiar with Chauncey's creepiness, throwing tantrums and crying loudly during the battle. However, Chauncey's existence begs a very tragic question: what happened to this baby?

5 Mario Meets The Desolation Of Smaug

The Ruined Dragon roaring in Super Mario Odyssey

Super Mario Odyssey finds Mario traveling to different kingdoms that resemble real-word locations such as Mexico, New York City, and Alaska. One kingdom, the Ruined Kingdom, takes inspiration from medieval England. However, this kingdom's glory has been lost to war, providing a dark backdrop for this pit stop on Mario's journey.

The Ruined Kingdom also features quite a memorable boss battle in the Lord of Lightning, a giant, hyperrealistic dragon who Mario must fight. For a series as cartoonish and whimsical as Mario, this dragon stands out as one of the most horrifying and fearsome creatures that players ever have to battle.

4 A Musical Jump-Scare

Mario being attacked by the Mad Piano in Boo's Big Haunt

The endless staircase isn't the only disturbing moment in Super Mario 64. What fans of the game might find more memorable is the frights from Big Boo's Haunt. This haunted house-themed level predates the horrors of Luigi's Mansion, and features many enemies that have imprinted themselves into the minds of 90s kids.

One of these enemies is the Mad Piano, who appears in one of the rooms of Big Boo's Haunt. While it seems like an ordinary grand piano, it reveals its true self when Mario comes near it. There's no greater jump-scare in video game history than seeing its lid pop open, revealing a mouth and teeth that chase Mario out of the room.

3 The Lost Ending To Luigi's Mansion

The unused morose Luigi face from the Luigi's Mansion E3 2001 trailer

Technically, this disturbing moment does not officially appear in Luigi's Mansion; however, it was teased prior to the game's release. In the Space World 2000 demo, as well as a trailer shown during E3 2001, a model of Luigi with a longer, depressed face appears, which certainly disturbed audiences at the time.

This model doesn't show up in the finished game, though data mining reveals where it may have been included. In an ending sequence displaying how well players did in their playthrough, a model of Luigi appears in data for each grade: great, good, and bad. The "bad" model features this long-faced Luigi sitting down, holding a flower.

2 The Dark Side Of Rogueport

The hangman's noose in Rogueport in Paper Mario The Thousand-Year Door

The Paper Mario franchise has featured a lot of disturbing details, from Mimi's transformation in Super Paper Mario to Count Bleck's backstory. However, no moment in this series takes the cake more than this subtle detail in Paper Mario: The Thousand-Year Door. Players don't even have to get too far into the game to find it.

In the opening town, Rogueport, players can notice gallows prominently featured in the center of town. Thankfully, the game doesn't go so far as to show this hangman's noose being used. However, it certainly seems to imply a dark and disturbing history for Rogueport that, so far, has been untold in the Paper Mario series.

1 A World That Wasn't Meant To Be Seen

Fire Mario in World -1 in Super Mario Bros for NES

The early Mario games, like any retro franchise, is prone to glitches that players can easily discover. One of the most popular glitches, not just in the Super Mario series, but of all time, is the hidden Minus World. By performing a trick right in World 1-2, players can be warped via pipe to this unintentional underwater level.

Unfortunately, once players make it to World -1, they're doomed. This underwater level loops forever, meaning players will have to lose all their lives or let the timer run out to escape this state of purgatory. It's a grim ending to Mario's earliest adventure, but it's a fun glitch that anybody can discover, even in ported versions of Super Mario Bros.

MORE: Inconsistencies In The Mario Universe