From the Super Mario Wiki
 Super Mario Galaxy
Penguru appears in four galaxies in the game Super Mario Galaxy. He appears in the Drip Drop Galaxy, the Bigmouth Galaxy, the Sea Slide Galaxy and the Grand Finale Galaxy. In the Drip Drop Galaxy, Penguru and several other penguins (of whom he is apparently the grandfather) appear on an island. They are distressed about the outbreak of Gringills (referred to as "Giant Eels" in the level name). He requests that Mario get rid of them and awards him with a Power Star when he does. Penguru's home is in the Sea Slide Galaxy on an island known as "Penguru's Island" where he lives alongside enemies. He is the keeper of one of the five Silver Stars that Mario has to collect in the Sea Slide Galaxy as well.
Penguru makes small appearances in the other two galaxies he appears in. In the Bigmouth Galaxy Penguru will appear at the beginning and tell Mario where to go. He often goes to the Bigmouth Galaxy to relax and think. Penguru's final appearance in Super Mario Galaxy is in the Grand Finale Galaxy where he is seen gazing up at Princess Peach's Castle. He is a tall penguin, similar to Coach, with a long gray beard, looking out into the sky.
 Penguru's Island
Penguru lives on an egg-shaped island (similar to a Yoshi Egg) that is suspended in the center of the water 'ring' that is the Sea Slide Galaxy. The top half is covered with sand, and patches of grass, whilst the bottom half is covered with shallow water. Penguru stands at the top of the island, which is flat, and covered in grass. The only way to reach the island is through a jet of water, that comes from a platform on the sea slide, after a valve has been spun down.
 Super Mario Galaxy 2
Penguru reappears in Super Mario Galaxy 2 in only two galaxies, the Hightail Falls Galaxy and the Cosmic Cove Galaxy along with his fellow penguins. In the Hightail Falls Galaxy, he is at the top of the large ramp and congratulates Mario and Yoshi for getting up there. In the Cosmic Cove Galaxy, he is seen standing on top of a platform near the waterfalls and appears in all levels. In the first level, he gives a helpful tip on how to get the star, and in the second one, he tells Mario about the twin falls.
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