ei ei mun!
Catchphrase of Umamusume's Matikane Tannhauser. Usually said with both fists clenched like the ganbaru pose but with arms spread further apart.
This phrase is memetic enough to overflow to the real-life Matikanetannhauser (the racehorse), with tweets of images of said horse being flooded with "Ei, ei, mun!" comments. Even NHK's official Twitter account has taken part in this.