Fast backtracking? *spoilers*

[MindfulOcean]

I can't beat Asgore with my punny never-hurt-anyone-ever character and I ate the pie early in the game not knowing it was special. I've read that you can get great armor in the Temmie village but it looks like that was way back early in the game. Is there a fast way to get there and back to the final boss?

[Lunarluck]

the elevators make it slightly quicker and use the boat keeper (obviously)

[FlaringK]

You have to send the Temmi to collags first and even than it's super expensive

[MindfulOcean]

Thanks for the help! I've completed the game now.

[Chara the Explorer]

As has been said, there's the elevators, plus the Riverperson is a fast-travel station.