Note: This is much easier after doing the first secret room (They all Float) when the clown doll is activated and then starting a new game after you've beaten it once.

When you first start the game from your bedroom just continue forward over the bear, after the tutorial pop up walk over it again to be safe. Afterwards continue walking over all the toys entering rooms as you go doing the same thing.

Once you get to the spot where the scene "Mr. Hopps??" appears you have to go back to your room and start from the bear again and once you go through all the rooms again and head downstairs and make it across the living room, the last doll should pop the achievement.

That's what worked for me and got my 100%. Good luck, I hope this made sense!