Hironobu Sakaguchi likened the development of "Chrono Trigger" to "play around with Toriyama's universe," citing the inclusion of humorous sequences in the game that would have been "impossible with something like "Final Fantasy"." When Square Co. suggested a non-human player character, developers created Frog by adapting one of Toriyama's sketches. The team created the End of Time to help players with hints, worrying that they might become stuck and need to consult a walkthrough. The game's testers had previously complained that "Chrono Trigger" was too difficult; as Horii explained, "It's because we know too much. The developers think the game's just right; that they're being too soft. They're thinking from their own experience. The puzzles were the same. Lots of players didn't figure out things we thought they'd get easily." Sakaguchi later cited the unusual desire of beta testers to play the game a second time or "travel through time again" as an affirmation of the New Game Plus feature: "Wherever we could, we tried to make it so that a slight change in your behavior caused subtle differences in people's reactions, even down to the smallest details ... I think the second playthrough will hold a whole new interest." The game's reuse of locations due to time traveling made bug-fixing difficult, as corrections would cause unintended consequences in other eras.