Undertale: The Lost Kids

Undertale: The Lost Kids is a CGI animated film by DreamWorks.

Plot
Fallen child Frisk teams up with all her freinds she met in the underground to rescue Undyne from Flowey.

As the story unfolds, Frisk discovers 7 lost children who own a time machine to reality which they use to their advantage.

Through hiding the truth until the last moment that Frisk wanted to kill them when she first saw her team, she manages to burn down 3 vines, recover Undyne and live on with her normal life on the Overworld.