Fir this trophy you need to collect the 4 items of clothing in the game. You cannot get this trophy before you finish Act 2.
Knit Cap: In the mailbox outside Strong Bad's house.
Data Boys shirt: From Bubs' Stand go left or right until you reach the Photo Booth. To the right of the photo booth is a cardboard box with the shirt underneath it.
Moustache: After you win the race go to The Track and go right until you find a microphone. Use it to see a cutscene of something falling out of a speaker. Go back to the starting line to find the moustache on the ground.
Red Chef's Hat: You can find this on top of the microwave in Act 2 after you get Homestar to leave the kitchen. I have written a quick guide on how to do this in the spoiler tags below.
*** Spoiler - click to reveal ***Check your e-mails.
Talk to Bubs about the free candy.
Go to the track to find the candy coupons near the benches.
Go back to Bubs to get the free candy.
Go to the Kings Castle.
Sneak in and take the shovel.
Get seen and get thrown out.
Go to Marzipans house.
Dig the patch of loose soil at the top of the screen.
Cover it in hedge trimmings (if you don't have any then use the shears on the hedge at the side of the house and pick up the trimmings afterwards.
Use the free candy with the Welcome Mat.
*Last chance to get
Go to the House of Strong and use Cell Phone on Homestar
Please vote positively if this guide was helpful and feel free to leave a comment if I can improve it in any way.