I couldn't find a walkthrough so I'm putting one here:

HQ:
Paper
Solve puzzle
Decrypted Message plus fax machine
Green poster
Insert code for IGC into fax machine
New paper
Money

Mall:
Vending machine
Center bottle
Fat man
Coffee plus character
Cup plus juicer

Milky Way:
Cone

Jurassic Planet:
Sickle
Horn

Planet Celery:
Warrant plus celery man
Door
Celery man
Sickle plus grass

Mall:
Grass plus juicer
Cup
Cup plus cone

Jurassic Planet:
Perfume plus character
Cone plus character
Bathroom
Wrench
Sink
Sink plus horn

Milky Way:
Wrench plus wheel

Mall:
Wheel plus fat guy

Jurassic planet:
Bathroom
Plunger plus toilet

Celery planet:
Manure plus discolored dirt
Horn plus fire
Rope plus cows

Milky Way:
Cows plus Farmer