-Estimated achievement difficulty: 3/10
-Offline: 35/35 (1000)
-Online: 0
-Approximate amount of time to 1000: 6-8 Hours
-Minimum number of playthroughs needed: 1 playthrough + Level replays
-Number of missable achievements: None
-Do cheat codes disable achievements? No Cheats
-Does difficulty affect achievements? No
-Glitchy achievements: None
-Unobtainable achievements: None
-Extra equipment needed? A second controller for cooperative based achievements.
Introduction
This Shrek game is a bit different than other ones you may have played. It focuses on being able to change characters whenever you want, and certain things require you to have two characters being controlled at once (local cooperative). This game has no difficulty settings to deal with. There are no glitches to deal with and the game's 1000 can be obtained easily.
Step 1: Complete the campaign
Focus on running through the campaign gaining the story related achievements, and early on putting in a 2nd controller to knock out the very easy cooperative based achievements as well as using each character's abilities. You do have the option of actually playing the game with a partner, if you choose to. You can gain a decent amount of collectibles on this run, but don't be shocked when you can't get certain things because you lack that specific ability. I suggest going to the store in the Ogre Camp and buying the Money Up upgrades to help out.
Step 2: Complete levels at 100% and buy all abilities and upgrades
Now you should have a good idea of how to complete the levels and should remember some chests/secrets you could not get to. Now that you have abilities you didn't have, you may get them. Look everywhere in the level, or in the forums if you're having a hard time with a couple of them. You should also grab any cooperative puzzles you haven't completed (there are only a few and listed in the guide).
Step 3: Mop Up
If you have any last upgrades you haven't yet bought, or anything else you forgot to do, go ahead and do so. This includes any character based or cooperative based achievements that may have slipped your grasp earlier in the the game.
Conclusion
This game is very easy and you should have no trouble gaining all achievements. The only annoying thing you may encounter is completing certain levels at 100%. Just keep looking and eventually you should find the last item(or items), or of course check the forum as most of the hard ones are covered when someone has a question on where one is located.