Where can I find every gnome?
Gnomes locations:
Behind Hopper's Cabin
In Forest Dungeon (East of entrance through pipes)
In Jungle between Lab and Quarry
In Jungle South of School
In School (Northwest)
In Corn Field
In Jungle West of Sewers
In Lab (Go through pipes in room Northeast of entrance)
In Sewers (First Room)
In Library (Eastern Room from entrance)
In House South of Graveyard
In Quarry (Southeast past bear)
Source: spreadsheet from reddit thread.
And this is video guide.