I have been a fan of SpongeBob Squarepants for years and think that the depth of the characters is one of the things that really makes this show work. Ever since I heard Mr. Lawrence say (in an audio commentary on the Season 1 DVD's) that Stephen Hillenburg based the 7 main characters on the 7 Deadly Sins, I couldn't help but be very fascinated. I think I've figured out which character is each one.
Sloth is the sin of laziness, or unwillingess to act. Obviously this is Patrick. He lays under a rock all the time and doesn't really do anything. In fact in the episode "Big Pink Loser" he got an award for doing nothing the longest.
Wrath involves feelings of hatred and anger. Squidward hates his life, usually hates SpongeBob, and is pretty much angry most of the time.
3. Greed-Mr. Krabs
Obviously Mr. Krabs is greedy and desires money. How could Greed not be Krabs? He actually sang about the power of greed in "Selling Out".
Plankton is envious of Mr. Krabs because The Krusty Krab is a success while The Chum Bucket is a failure. His envy drives him to try to steal the Krabby Patty secret formula.
I actually think this one is pretty funny. Did you ever notice the running gag in Spongebob where they say "don't forget to feed Gary" or Sponge says "I gotta go feed Gary". Gary even ran away that time when SpongeBob forgot to feed him. Glutony usually refers to the overindulgence of food so I'm guessing this one fits him pretty well.
Sandy takes a lot of pride in who she is and where she comes from. She takes pride in the fact that she is from Texas and likes to let everyone know it. She also takes pride in the fact that she is a mammal and a land creature, like in the episode "Pressure" where she tried to prove land critters were better than sea critters.
Ok, I know what your thinking. It does seem a little weird and curious at first but I have given it a lot of thought. Lust in one definition is "excessive love of others". I think this one works best for Spongebob. He shows his love of others with his overeagerness to do good and help people. If anything is true about SpongeBob its that he loves everyone around him, even if they don't exactly love him back.
So this is what I came up with. I don't know what anybody else thinks. Oh by the way try not to analyze cartoons too much, especially SpongeBob. I actually think the people on the show try to be inconsistent on purpose. Just to be funny.
(not my words... copy and pasted from elsewhere)