Here is the full list of all 20 Nyan Cat: Lost In Space achievements.
Ran 25 seconds without collecting any food
5 pills collected in a game
Played 10 times on Nyan Cat City theme
x250 score multiplier reached in a game
Tac Nayn touched 9 times
Ran 1000 meters without touching any kind of enemies
Stayed on the highest platforms at least for 30 seconds
Played in a world other than Space
Stayed on the lowest platforms at least for 30 seconds
5 times jumped over a doggy in a game
100 bombs deactivated
Played with a skin other than NYAN CAT
A UFO abduction survived
A UFO abduction survived 100 times
42195 meters completed
2000 bombs deactivated
20 enemies eliminated with Nyan Love
250 enemies eliminated with Nyan Love
100 Cow items collected
Jumped on Gold Platforms 1000 times