Nice!

Find hidden photo.
***MISSABLE***
In the Bedroom, "Examine" the Photo of Linda which is sitting on top of the Dresser, to the right side. When zoomed in on the photo, "Use" the Photo to uncover a secret compartment and unlock this achievement.

No Wonder He Misses Her.

Examine Linda's self potrait.
***MISSABLE***
In the Bedroom, "Examine" the large Painting on the wall above the Dresser and this achievement will pop.

Clog The Bog!

Put Toilet Roll in the loo.
***MISSABLE***
In the Bathroom, pick up the Toilet Paper, on the floor just to the right of the sink, then "Use" the Toilet Paper on the Toilet to clog the toilet and unlock this achievement.

Yo, MF! You Better Listen To Me!

Make Marlo perform.
***MISSABLE***
In the Bedroom, pick up the Microphone from the top of the dresser (between the left and middle photo frames) then head over to the Living Room. In the Living Room, use the Microphone on the Stereo, located on the shelves to the right of the TV, below a picture of Linda (second shelf down from the top). Marlo will perform a little freestyle (dropping an F Bomb) and this achievement will pop.

Glad That's All Over!

Defeat All Shapes.
To earn this achievement you must "Defeat All Shapes", or rather defeat all forms that Marlo changes into (Ice, Slug, Cat, Shark).

To defeat the Ice form, grab the Hair Dryer (located in the Bedroom, on the floor, leaning up against the right side of the Dresser) and the Batteries (located in the Kitchen, on the counter to the left of the Salt. Then use the Batteries on the Hair Dryer and then use the Hair Dryer on Marlo while he is in Ice form to prevent Marlo turning into an Ice cube again.

To defeat the Slug form, grab the Salt (located in the Kitchen, on the counter to the right of the Batteries and the left of an apple?), then grab the Empty Glass (located in the Bedroom, standing on the end of the bed) then use the Salt on the Empty Glass in your inventory (to obtain the item Glass with Salt). Then head into the Bathroom and use the Glass with Salt on the Sink to obtain the item Salty Water, lastly use the Salty Water on Marlo while he is in Slug form to prevent Marlo turning into a Slug again.

To defeat the Cat form, grab the Spray Bottle (located in the Bathroom, on the end of the bath, at the opposite end of the taps) then use the Spray bottle with the Sink to fill it up. Then use the Spray Bottle on Marlo while he is in Cat form to prevent Marlo turning into a Cat again.

To defeat the Shark form, examine the Photo of Marlo and his Dad (located in the Bedroom, on the right side of the Dresser, opposite the Photo of Linda), when zoomed into the Photo, "Use" the Photo to reveal a secret compartment and grab the Key. Then travel to the Living Room and use the Key on the Boxing Gloves (located in the Living Room, on the shelves to the right of the TV, on the top shelf, above the Stereo). Then use the Boxing Gloves on Marlo while he is in Shark form to prevent Marlo turning into a Shark again.

Once all 4 personas are defeated, this achievement will pop.

I Hate Post-credits Scenes!

N/A.
Once you cure Marlo of his four alternate personas, a cut scene plays and then the credits roll. The game however is not over, after the credits you are back at the main menu, that now looks notably different, hit the Play button once again to continue that game, as soon as you do this achievement pops.

Prickly Prank.

N/A.
***MISSABLE***
To earn this achievement, grab the Cactus (located in the Living Room, on the Shelves to the left of the TV, 3rd shelf down), any items remaining in your inventory from your first playthrough remain in your inventory, so if you grabbed it earlier, fear not it will still be there. Then go to the Bedroom and use the Cactus on the Bed and the achievement will pop.

Best One of the Day.

N/A.
***MISSABLE***
To earn this achievement, grab the Cigarettes (located on the table under the TV in the living room) then use them on the Toilet in the Bathroom.

Take My Call.

N/A.
To earn this achievement you must locate two pieces of paper, to find the first, go into the Kitchen and "Examine" the Pin Board, the second piece is found by "Using" the Dresser in the Bedroom. With both pieces of paper in your inventory, use one with the other to combine them, then use the Phone Number with the Charging Phone found in the Living Room on the Shelves to the right of the TV, on the bottom shelf and the achievement will pop.

That Wasn't So Bad Was It?.

N/A.
After completing the second half of The Mind of Marlo, this achievement will pop after the credits have finished rolling.