Find 4 hidden photos
This achievement requires that you find 4 out of the 7 hidden photos in the game. The photos are hidden within the background of a few of the levels. They look like wallpaper that is peeling off a tiny bit. You must simply tap the peeling area with your finger to collect the photo. The locations of each photo are given below (thanks to TNTJudBud). As soon as you find 4, the achievement unlocks. You can exit each level as soon as you find a photo as you do not need to complete the level to save the progress.
1. Magnifying glass - Level 1-14. It's on the top left side of the stage.
2. Candy beaker - Level 2-19, above the second star.
3. Books - Level 3-19. It's on the far right side of the stage
4. Facebook - 'Like' the Cut the Rope Facebook group using the link in the Professor's Album for this photo. You do not actually have to like the page or even have a Facebook.
5. Robot - Level 4-7. It's in the upper part of the level. Down and to the right of the green monster
6. Bath Time - Level 5-23. On the right of the level.
7. Om Nom And A Cactus - Level 6-17. It's found on the middle right of the level specifically the left hand side of the second robot.