All the achievements that aren't exactly what it says on the tin (or label in the walkthrough) or something you will most likely get without even trying.
31) Thirsty - Drink some water
32) Save the Whales - Drink all the water
* These two are done with the water bottle next to the hamster wheel in your Home.
36) One... - Go once over the wheel
37) Two... - Go twice over the wheel
38) Three... - Go three times over the wheel
39) Four... - Go four times over the wheel
40) Five! - Go five times over the wheel
* How to: Get on the hamster wheel, run it till it's at max speed, stop running, whoosh.
46) Corpse Loop - Get a corpse into an infinite loop
* Panic Button ftw.
126) Relapse - Panic while touching a checkpoint
* Is occasionally buggy, but just hit Panic a few times on every floor until you get it.
128) Clicky - Click click clickaroo
* Cliiiiick.
133) So Happy! - Make a happy face with keyboard letters
* Very annoying on keyboards that aren't of the default English layout. Just keep hitting the keys.
136) Waltzing Ma - Push the tilda key (~)
137) Partial Colon - Push the semicolon
* Also annoying on different keyboards. Keep pressing those buttons.
144) Ode to Joy - Play Ode to Joy on the Piano
145) Twinkle Twinkle - Play Twinkle Twinkle (Little Star) on the Piano
146) Row Row Row Your Boat - Play Row your Boat on the Piano
* E, E, F, G, G, F, E, (D)
* Low C, low C, G, G, A, A, G
* Low C, low C, low C, D, E
153) Fort Alpha - Find Hidey Hole 1
* Lower middle of first floor, in the "room" "blocked" by a launcher.
154) Fort Beta - Find Hidey Hole 2
* Upper left of first floor, under the spikes.
155) Fort Gamma - Find Hidey Hole 3
* Middle of second floor. Straight to the left of the respawn point.
156) Fort Delta - Find Hidey Hole 4
* Upper left part of second floor, in the lower of the two long paths.
157) Fort Zeta - Find Hidey Hole 5
* Upper left part of third floor, in the hard to reach half-room.
158) Fort Eta - Find Hidey Hole 6
* Right side of third floor, in the lower of the indentations in the wall.
159) Fort Theta - Find Hidey Hole 7
* Middleish of fourth floor. Jump straight up and go right from the respawn point.
160) Fort Iota - Find Hidey Hole 8
* Upper right part of fourth floor. Right under those spikes in the "tough to jump to" spot.
161) Fort Kappa - Find Hidey Hole 9
* Fifth floor, upper right part, pretty much where you will land if you manage to avoid the spikes by the elevator launcher.
162) Fort Lambda - Find Hidey Hole 10
* To the lower far left on fifth floor. Really, it's almost too obvious that there is something in that spot.
177) RGB - Stop the reels on Elephant, Llama, Giraffe
* If you hadn't caught on: Elephant = Red, Llama = Green, Giraffe = Blue, and Emu = Yellow.
192) EleClick - Hey, that tickles!
* Click the elephant.
193) Won't Follow Directions - You just had to do it...
* Right click the game, disobey the "Don't Click Here".
202) I Can't Live With This - Die outside
* Took me a while to remember the panic button here.
204) Two Browser Windows - Open two browser windows of the same game
* The same game being Achievement Unlocked 2. Oh snap!
205) Break Time! - Find the hot coffee feature
* This will make sense once you do the above.
213) The Final Straw - Stand on top of the straw
* In the secret secret room accessed from the coffee feature.
221) Hey, a Pastry! - Poop a Pastry
* Spacebar.
235) Aww Poor Puppy - Look hopeless
* I think you just have to stand around for a bit, not 100% sure on this, though.
Thar. That should be all the not-so-obvious ones. Now stop asking already! D: