Video game adaptations used to mean dressing up attractive actors in iconic costumes and trying to stuff 20 hours of gameplay into a 90-minute movie. It didn’t really work. Now, video game adaptations are more reliant on CGI versions of favorite childhood characters appearing both realistic and either terrifying or adorable. It’s the difference between Angelina Jolie as Lara Croft in Tomb Raider and recent films like Rampage.

Detective Pikachu director Rob Letterman knows how important nailing the CGI adaptation of beloved 2D characters is to ensuring longtime fans are on board. Getting it right leads to praise for a thoughtful reworking of a character like Pikachu or Bulbasaur. Getting it wrong, unfortunately, leads to the Sonic the Hedgehog fiasco.

The Verge caught up with Letterman shortly after news came out that Sonic the Hedgehog director Jeff Fowler announced Sonic would get a redesign in Paramount’s live-action adaptation, following intense backlash online. Fowler didn’t suggest if the film’s release date would be pushed back to accommodate the overhaul.

Letterman told The Verge he “just heard about the Sonic situation 15 minutes ago,” adding he didn’t envy the position that Fowler and Paramount have found themselves in. Deciding to alter a main character’s design just a few months ahead of its scheduled release probably wasn’t easy to do, Letterman says. Although he couldn’t speak to Fowler or Paramount’s process into reworking Sonic’s look, he did offer some insight into how impossible it would have been for his Detective Pikachu team to take on such a dramatic undertaking.

“There’s no right or wrong to how you make one of these movies,” Letterman says. “It would be very difficult for us to redesign anything. We spent a year designing all the characters ahead of shooting so that we could get it all right. If we were off by an inch on Pikachu, [actor] Justice Smith’s performance would go right out the window. For us, it would have been impossible — but that doesn’t mean they can’t do it. I wouldn’t want to be in their shoes — they’re in a difficult spot.”

To say that Letterman and his team were obsessed with ensuring they did justice to game designer Ken Sugimori’s original pokémon illustrations is an understatement. They knew Detective Pikachu had to do more than pay homage to the creatures that evolved over the last three decades into a global phenomenon; they had to treat each design with the same respect they gave human actors.

“I wouldn’t want to be in their shoes — they’re in a difficult spot.”

The design team behind Sonic the Hedgehog wasn’t so fortunate. Whereas adaptations of Pikachu and Psyduck in Detective Pikachu found a way into hesitant fans’ hearts, Sonic’s bizarre appearance struck fear into the hearts of blue hedgehog stans. His lanky, human legs combined with a mouthful of disturbing human teeth juxtaposed with his overall alien physique is uncomfortable to witness. It also begs the question: how could one movie seem to get it so right, while another got it so undeniably wrong?

Letterman credits much of their design decisions to spending two years studying different animal designs and collaborating with the Pokémon Company design team in Japan to ensure everything worked.

“We studied a lot of animals and how they behave and how they interact to ensure we got it right,” Letterman says. “Bulldogs, in particular, for Bulbasaur and how they act in packs or how they get you to pay attention. There’s an extraordinary amount of craft that went into making the movie on the animation side as we tried to bring everything to life.”

It worked. Detective Pikachu might have its flaws, but its depiction of pokémon is one of its biggest strengths.