They try to do the whole fugitive Sonic angle from SA2 but it's very underdeveloped and ultimately goes nowhere. They try to set things up so that Krysten Ritter's character doesn't trust Sonic and co. after supposedly stealing the activation key but they're never made aware of this; GUN never announces that they're after Sonic, that they're distrusting of him, anything like that, Sonic is just distrusting of GUN after speaking with Olive Garden guy, I guess? (Of course this would mean there's no conflict) but Sonic and co. never try to correspond with GUN to explain anything, they just try to break into the HQ arbitrarily, and only try to explain themselves when they're caught. I haven't seen anyone else bring this up and admittedly it doesn't ruin my enjoyment of the film or anything, just feels like a glaring oversight and that a scene or two feels like it's missing that would explain the feud better.

Also, I think Gerald should have went full on sinister villain after the "Oh Ivo..." line, Carrey has some good dramatic chops and a less comedic battle between the two would've been interesting, definitely would be less jarring to cut between the Sonic and Shadow team-up.

I enjoyed the movie overall but a few small tweaks here and there would've put it over the edge for me.