1) Chu-chu Nezumi
Up a tree to the left of the Stotch house - shoot it down with a ranged weapon.
Hiding behind the trees to the right of Kyle’s house.
Hanging from the right-hand side of the Tower of Peace first floor during the 'Mongolian Beef' side mission (obtained from Mr. Kim in City Wok) - shoot it down with a ranged weapon.
In Butters’ bedroom, upstairs in the Stotch house.
Inside Cartman’s garage - get the key from the drawer in Cartman’s front room.
[MISSABLE] [Day 3] During the ‘Beat Up Clyde!’ quest, use the probe on the upper level of Clyde’s fortress to teleport to the top balcony.
[Day 3] Behind a vent inside the South Park Gazette - use your Gnome Dust power to get inside it.
[Day 2] Use the probe on the side of the Community Centre to teleport into the basketball court.
[MISSABLE] [Day 3] During the ‘Unplanned Parenthood’ quest, after destroying the mounted gun in the corridor use your Gnome Dust power to go through the tunnel and get behind the rubble.
[Day 2] Down in the sewers next to Mr. Hankey’s house.