There are five Hidden Trophies, They are in the form of Snowmen.
They are found in the following levels;
Level 5-3 - Snowman in the top right corner.
Level 5-5 - Snowman in the middle just under the cliff.
Level 5-9 - In the big group of snowmen in the middle.
Level 5-14 - Snowman at the top by the fir trees.
Level 5-19 - Snowman, top left corner.