Here is the full list of all 13 Little Ninja achievements.
Fell Into The Molten Model
It's Spatuala, AND A Katana!
Played (Big Boom Boom Space Ring Game) Theme On Piano (If you still don't know what I mean, take the word aloha, remove an a, and mix up the letters a bit)
Read Adam's Sleep Deprived Message
Use Boost 50 Times
Use Boost 250 Times
Focused 50 Times
Get Caught 30 Times
You Tried, And That's What Matters!
Win Against Matt In Ping Pong
Ribbit Ribbit
Break Into The Break Room