The novelty items are story related, so you can't really miss that achievement.
*** Spoiler - click to reveal ***
Upstairs in green tentacle's room push the on/off button for the stereo. Push the speaker in the middle of the room to make the fake barf fall from the ceiling.
Get the disappearing ink in the second room on the first floor with the depressed salesman.
In the past get the letter from the letterbox in front of the house and send it to Bernard. Have Bernard give the salesman the letter and he'll open the door.
Get the gun with the flag and go downstairs.
Pick up the fake barf and go through the double doors. To the left of the chimney is a grating. Open it.
Go right and chase the teeth from the vat-o-teeth to the open grating and pick them up.
Follow the instructions to to get the laughing box (get Laverne to send Bernard her scalpel and cut the clown with the scalpel).
Exchange the gun on the table to the right of the table with the flag gun and ask the salesman for a cigar.
You should now have
disappearing ink
fake barf
a lighter gun
chattering teeth
a laughing box
an exploding cigar
and the unlocked achievement.