This is how Celebrating Mac's victory and Ending goes in The Impending Duel.
[Then we see everyone in the Great Hall]
Stoick the Vast: Everybody, let's celebrate Mac's victory! I declare that his impending duel against Mesogog is now over!
[Everyone cheers as they chow down their dinner]
[Then Mac walks to Twilight]
Mac Grimborn: Twiley-kins, I just want to say I'm sorry. I know that I had to duel Mesogog in order to prevent him from hurting innocent people, but... there was something in me that wanted to fight him. I promise, I won't leave your side or ruin our relationship.
Twilight Sparkle: No, Mac. He forced your hand. You did what you had to do.
Mac Grimborn: I know. That's why I wanted to say sorry. Can you forgive me?
Twilight Sparkle: Of course, Macsey. I will always forgive you, my one true love.
[Then they kiss as Tuffnut gasps]
Discord: Ah, romance, ex-machia, but... Two thumbs way up!
Starlight Glimmer: This...
Trixie: Changes...
Thorax: Everything.
Mac Grimborn: There's still that must be done, and I promise I won't jeopardize our mission again.
Tuffnut Thorston: Mesogog might be gone, but Grogar and his Legion of Doom are still out there.
Ruffnut Thorston: Tuff's right. And until they're defeated, no one's safe.
Snotlout Jorgenson: Yeah, I mean, Mac's dealt with one of the toughest, evilest, most ruthless villains in the world.
Fishlegs Ingerman: And defeated! Yeah.
[Everyone agrees as the film ends]