In Paper Mario, star pieces are found in bushes, on the ground, on boxes, under flip panels, or are given to Mario by people. There are 160 star pieces in the first Paper Mario game. Some of the star pieces are given to Mario via a flip panel. These panels are only flipped when Mario uses the Super Boots, Ultra Boots, or the Ultra Hammer near the panel. Using the I-Spy Badge, Mario can find these panels much easier. Each star piece has no actual value, but they can be given to Merlow at Shooting Star Summit. By speaking with him, Mario can gain access to his shop. This shop sells badges, like Rowf's, but the badges here cost star pieces instead of coins. The price of each badge ranges from 1 to 20 star pieces.
In the second Paper Mario game, star pieces are given to Mario in all of the same ways as in the first game. One of the only differences between these two games' star pieces is that TTYD only has 100 rather than the 160 in Paper Mario. Later on in the game, Mario finds a person named Dazzle in the Rogueport Sewers. Dazzle provides the same job Merlow did in the last game. He is found outside of Merluvlee's house in the eastern side of the plaza in the sewers. She, too, has many badges to sell with many prices ranging from 1 to now 25 star pieces each.
Eastern and Central Rogueport
The Roof of Zess T.'s house in Rogueport.
In the alley, directly behind Zess T.'s house. - Flip Panel.
Behind Professor Frankly's house, on a couple of crates.
House owned by a bandit behind the Inn in Rogueport.
In front of Professor Frankly's house - Flip Panel.
Behind Crates near the east exit of the Rogueport Plaza.
Behind of the barrel near Ishnail's home.
Near the very front of town in the harbor. - Flip Panel.
Use the paper boat at the harbor to access a hidden area.
Around the Chimney of Bobbery's house.
On the roof of a building in eastern Rogueport - Flip Panel.
Along the wall as you enter.
Behind the tall warp pipe.
Behind the warp pipe used to get to the blimp.
In front of the Pianta Parlor - Flip Panel.
Behind the trashcan by the item shop on the west side of town.
To the left of the Excess Express - Flip Panel.
Upper Rogueport Sewers
Behind Pillar by Merluvlee's house.
Inside of Herb T.'s house - Flip Panel.
Behind the Pillar on the other side of the large plaza.
Behind Fallen Pillar next to Merluvlee's home.
Next to the Eastern Rogueport entrance - Flip Panel.
Near the entrance of Boggle Woods - Flip Panel.
In the background of the room that leads into Petal Meadows: Use spring jump to access the pipe.
In the background of the western side entrance via the drain topside.
Enter through the sewer drain.
Lower Rogueport Sewers
Behind the stairs that lead into the room with the Pit of 100 Trials.
South of the Thousand-Year Door - Flip Panel.
In front of the Black Chest that gives Mario the plane ability - Flip Panel.
To the room to the right of the Thousand-Year Door, behind the big block.
Petal Meadows, Petalburg, and Shhwonk Fortress
Hit the tree near the very beginning of the Pedal Meadows.
To the right of the blue switch located in the background in Pedal Meadows.
Near Bub-ulber in Petalburg - Flip Panel.
Near the pink flowers in the town - Flip Panel.
In the very first bush past Petalburg on the way to Shhwonk Fortress.
Near one of the castle keys, behind the bars - Flip Panel.
To the right of an open window.
After it has been elevated, on one of the yellow blocks.
To the right of one of the Paper Airplane spots inside of the later parts in the castle.
Use the bigger purple block to elevate you into an area leading into a different room.
Boggly Woods and the Great Boggly Tree
Near the blue switch that raises up a warp pipe.
Inside one of the trees in the area of Flurrie's house.
Next to the sofa located in Flurrie's house - Flip Panel.
Behind the fence by the warp pipe that is used to enter Flurrie's home.
Behind warp pipe that leads into the prison cell.
Inside of the prison cell colored blue - Flip Panel.
In a bush while trying to catch Lord Crump.
Behind the warp pipe in the room with the very large tree stump.
The first big bush near Pugnent's shop.
In the very first room of the tree. - Flip Panel.
To the right on one of the flights of stairs in the arena's entrance - Flip Panel.
First floor of the storage room - Flip Panel.
In Grubba's desk.
Behind the telephone booth.
Behind the plant that is in Grubba's office.
In front of the blimp - Flip Panel.
Behind the yellow block in the upper floor of the storage room.
Behind the counter in the juice shop.
Under the billboard that is located just above the juice shop outside.
To the right of Arena's entrance, behind the ferns.
In-between the first two houses of the town.
Behind a bush in the west side of town.
Behind the barrels in the fenced-in area of the east side of town.
Twilight Trail and Creepy Steeple
Behind the tree that has fallen down.
Right behind the warp pipe after this tree.
Behind the wall in front of Creepy Steeple.
In the small hole in the very beginning.
In the room with the parrot's key - Flip Panel.
On the right side of the room with the moving staircase - Flip Panel.
Passed the room where Mario frees the boos.
Keelhaul Key and Pirate's Grotto
Near the right side of the coast line - Flip Panel.
At the cliff on the right side of the island.
Left side of the beach in Shantytown, the makeshift town near the beginning - Flip Panel.
Behind the first bush after the town.
On the right side of the beach in Shantytown, behind some rocks.
By rocks near the Pirate's Grotto's entrance.
On platform by the spikes that spout out from the floor.
Inside of a barrel in a tall room with many, many barrels.
Above the waterfall inside of the Pirate's Grotto - Flip Panel.
Behind a locked door, in the middle of a room with many Para buzzies- Flip Panel.
Excess Express, Riverside Station, and Poshley Heights
By the seats in Cabin 4 - Flip Panel.
In drawer in Cabin 5.
Inside of the engine of the train - Flip Panel.
By returning the pot to Chef Shimi.
By returning the ear rings to the waitress aboard the train.
Behind the cylindrical object by the storage room key in the Riverside Station.
Behind the Pink house, go through the hedge.
Right in front of the Excess Express in Poshley Heights - Flip Panel.
Behind the lawn chair near the blue house.
Left of the hotel, in the hedge.
To the left of the warp pipe used to enter this area - Flip Panel.
Behind the shrub in the next area.
Behind part of the crumbled wall near the entrance to the actual town.
In the western part of the town, behind a wall.
Left of the cannon statue - Flip Panel.
Behind boxes in the far right house.
X-Naut Fortress and The Moon
Use the crank to obtain some items, one of which is a star piece.
On the far left end of the air ducts.
On the Moon, in the crater, in the area where the X-Naut Fortress is visible - Flip Panel.