Derpy squinted her eyes and examined the date that the wedding for Cranky and Matilda was scheduled. With a smile, she wrote down and published the invitations with the correct date.
Meanwhile, the girls stood in position as the Bugbear arrived on the scene. They came together, glowed brightly, and deluged the monstrous beast with their friendship magic, leaving nothing more than a smoldering pile of ash where the monster was.
"Too easy. They've really gotta start giving us challenges..." said Twilight as she cleaned up the dust with ease.
This implies that Derpy had sent the invitations after the Bugbear had appeared. However, we know they had been published before the Mane 6 started fighting the beast, and I don't think Cranky and Matilda would have sent the invitations on the day before the wedding. Therefore, there should be a timeskip between Derpy correcting the invitations and the Bugbear appearing.
Could have at least shown the background ponies. The flower girls not panicking and The Doctor getting his suit tailored