The End of Flutter Valley (2) - S1-E2
Other mistake: As the Stonebacks begin to destroy the bridge the Ponies call out for help. As the bridge moves up and down, locks of Gusty and Baby Cuddles' hair flash white. Baby Cuddles is also drawn in a deformed fashion with no neck and two rumps.
Moero! Pegasus Ryuseiken - S1-E2
Other mistake: In the ending shot of the tournament bracket showing the potential future opponents, the two saints' names are written the wrong way, as "DORAGON" and "ANDOROMEDA", instead of Dragon and Andromeda. (00:22:00)