Personally, I don`t regard this as the "real" storyline. At least not considering the events that happened in The Lion King.
When it comes to Timon and Pumbaas backstories, and Simba growing up in the jungle, that I can believe. But other than that I regard TLK 1 1/2 as more of a parody/spinoff of the original film.
The storyline is just way too silly to make any sense... It`s just a spinoff of the original told from Timon and Pumbaas "hilarious" point of view.
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Sorry for the rant, I just dislike this movie.