Here is the full list of all 16 Yappie! Knockout achievements.
Qualify from your first round
Qualify from 100 rounds
Qualify from 500 rounds
Qualify after a round goes to overtime
Qualify from a racing round despite falling over more than 10 times
Qualify from a team game with a score of 1
Qualify from a round without falling over even once
Get first place in a racing round 5 times
Get first place in a racing round 20 times
Win your first Game
Win 5 Games in a row
Win 7 Games
Win 20 Games
Clock up 1 hour total time falling
Knock someone over