Big Penguin's Iceberg

Big Penguin's Iceberg is an unused course used for experimental purposes only found in some personalized copies of Super Mario 64. It can be found in the basement after completing all of the stars for Shifting Sand Land, which removes the course entirely and replace it with Big Penguin's Iceberg. The level is infamous for the return of the penguins of Cool, Cool Mountain.

Overview
The map is very similar to Cool, Cool Mountain and Snowman's Land, but it's way flatter compared to Cool, Cool Mountain. The map is around the same size as Snowman's Land. It has four enemies that can be found at the level. Spindels, Frozen Amps, Blue Goombas, and the Mr. Blizzards.

The course has the same skybox as Cool, Cool Mountain, and it is surrounded by towering icebergs and an endless ocean.

Landmarks
The landmarks that can be found here are similar to other courses found in Super Mario 64.

The Mountain
At the left corner, there is a huge mountain similar to Tall, Tall Mountain, but smaller. There are two branching pathways found at the mountain. Mr. Blizzards and Spindels that can be found at the mountain as well. You can get the first and fourth star here.

The Cold Cave
At the right bottom corner, there is a big slippery hill with a tunnel that leads to The Cold Cave. You can get the second star here. The penguins can be found at the top of the hill.

Ice Rink
At the left bottom corner, there is a freezing lake with ice physics. Unlike Snowman's Land, the lake does not use the lava retexture. It uses the Hazy Maze Cave gas, as it slowly kills Mario, turning him blue the longer he stands on the lake. You can get the third star here. The lake is also near by the ocean. It uses the Shifting Sand Land quicksand retexture. It is not a good idea to touch the ocean.

The Crevasse
The Crevasse is a huge gap found at the right top corner of the map. Going into The Crevasse can send the player to a segment of the level, where you can get the last star here.

Missions
''These are the missions that can be found in Big Penguin's Iceberg. Since this course is so obscure, remember to take these missions with a grain of salt.''
 * 1) AVALANCHE ACTION!
 * 2) STAR INSIDE THE COLD CAVE
 * 3) 8-COINS AROUND THE ICE RINK
 * 4) SCALING THE TOWERING TUNDRA
 * 5) DEPTHS OF THE CREVASSE
 * 6) 100-COIN STAR

Avalanche Action!
Avalanche Action has Mario climbing the mountain similar to Tall, Tall Mountain's mountain. The father penguin doesn't appear in this one. Anyways, there are two pathways. Choose the right path to get to Avalanche Action's second part. This part has boulders from Hazy Maze Cave, but retextured with the Mr. Blizzard textures. Make sure to dodge all of them, since getting hit by one will cause Mario to slide down to the bottom of the mountain, which should kill Mario from the fall if he doesn't land on the small patch of snow. After you got past the snowballs, grab the star. However, after getting the first star, the father penguin comes back and never leaves again, similar to Jolly Roger Bay's strange function.

Star inside the Cold Cave
To get the star, Mario must traverse into the ice cave from the tunnel on the hill. The cavern consists of three enemies. Blue Goombas which is probably a reference from SMB1, Frozen Amps which is a blue slow variant of the normal Amp, and the Snowmen. Hazy Maze Cave's theme plays in this part of the level. You must jump across tedious platforms that fall after around 2 seconds (similar to donut platforms), and do double jumps to gain enough height to reach the ledge. Afterwards, grab the star.

8-Coins Around The Ice Rink
Like every 8 Red Coin star, you must find the 8 Red Coins. However, The location of the 8 Red Coins is at a freezing lake, similar to Snowman's Land's freezing lake. However, unlike the common freezing lake, the lake slowly takes health away from Mario the longer he stands on it. Mario must collect all 8 Red Coins around the ice rink and get the star at the center before he dies from frostbite.

Scaling The Towering Tundra
Continuing the adventure up the mountain similar to Tall, Tall Mountain's mountain, you must take the right pathway instead of the left. You must long jump across pits, backflipping to grab onto the ledge, and more to climb the mountain. After reaching the top, You can see everything from up there. However, The Snowman from Snowman's Lost His Head in Cool Cool Mountain returns, but much bigger than before. He states that he's about to go to Snowman's Land, and grants Mario a Power Star for meeting up with him. After that, you would need to restart your entire game just to see him appear again.

Depths of The Crevasse
Similar to Cool, Cool Mountain's special segment, Cold, Cold Crevasse, This one is much huger. Fall into the crevasse, but make sure to slowly get dragged down by the slope to not deal too much damage to yourself. Afterwards, You can explore what seems to be a small and not so confusing maze, unlike the basement of the.. sacred build. Anyways, the same enemies from the ice cave are here, too. The layout of the crevasse is similar to the ice cave as well. After reaching the end of the deep crevasse, grab the star.

100-Coin Star
You know what to do here. Collect the 100 coins that can be found in the level, then grab the star.

Theorizing
The level itself could've been all a test created by the developers of Super Mario 64, seeing what the Personalization A.I. can generate from the game itself so far. This level never made it into release since it was only for experimental purposes, but the Personalization A.I. will sometimes add the level into the copy for players that have gotten to the Castle Basement in only 20-30 minutes or just some pro player, as A.I. studies the player's playstyle.

Super Mario 64 Lore Connection
This refers to the images of Super Mario 64's Lore. For example, When you get rid of Big Bob-omb, there are three rolling balls now.

In this case, this most likely refers to the Snowman from Snowman's Lost His Head in Cool, Cool Mountain. When you see him in this level, he is huge compared to the last time you saw him. He grants you a star and supposedly "goes to Snowman's Land". When you see him in Snowman's Land, he is the size of a literal mountain. He calls you a snow flea, then attempts to blow you off with the wind coming from his mouth hole.

Footage
This image consists of the Big Penguin's Iceberg's Star Select screen. Unfortunately, the youtuber has privated all of his videos, along with the footage. This singular image still stands to this day, however.