These cannot be missed

• Amuse-Bouche - Level 1
  
• Houston, we have a problem - Chapter 2
  
• It Came From Outer Space - Chapter 3
  
• Getting the Boot - Chapter 4
  
• Eat the solar system - Final level

To earn a medallion in a level, you will have to eat almost everything you can and get both of the Blob Friends. There is no time limit, and you can die as much as you like. However, you cannot always go back (like in pipes or in rooms with advancing lasers)

• Not too Shabby - Earn a silver medallion or better in five levels
  
• Golden Blob - Earn a gold medallion in every level

• Graduation Dinner - At the end of the Chapter 1, eat everyone at the graduation party
  
• Delicious Magnetic Balls! - Right near the end of the last level of chapter five (Army Base level 20), you will see a spike pit with four small floating magnets above it. Jump across and consume them all for this one.
  
• Jealous? - Go to leaderboards and check out the top score
  
• Finally, monsieur, a wafer thin mint - Absorb 1,500 items. You will get this as you play.
  
• Complete all mini-game levels - There are four mini games levels, one at the end of each chapter.
  
• Extinction - Eat all 10 of the escape pods in the final level (Tip from TheMachineK1ng - if you mess up you can self destruct to try it again instead of restarting the level)

• Blob Friends Forever - Each level has two Blob Friends to find (except the mini games which have one)

For a complete guide to the location of all the Blob Friends, there is a great guide here.[www.playstationtrophies.org]

Information stolen from

• Basic guide[www.xboxachievements.com]
  
• Full guide and friend locations[www.playstationtrophies.org]