Basing all of this off of how the characters were originally, as now most of them are pretty much untypable.
Spongebob: ESFJ 2w3 (ENxP & ENFJ typings are just downright wrong. First off, he's definitely not an Ne dom. Ne doms generally take their intuition much more seriously and use it as their main approach to life (Along with their Fi/Ti, neither of which I see very much of in Spongebob), whereas Spongebob seems to only tap into it while having fun (Albeit having fun A LOT), or when it's really needed, showing his Ne to be Tertiary. Rather he cares for others, readily shows his emotions, and is willing to make great sacrifices for others, showing Fe. He also uses Ne over any sort of a Ni, and has clear Si with no visible Se, disproving ENFJ. He is very loyal to his job, friends, and way of life, and looks to the past to see how things have always been done, or what he's been previously told, and uses this information to solve problems, showing Si. When he's at his worst, he becomes selfish and begins doing things alone, stops caring about others needs, and begins blaming others and throwing out accusations, feeling distrustful towards them. Inferior Ti).
Patrick: ISTP 9w8 (I really don't see where he would be an ISFP, he seems very Ti > Se in his ways. There is a small chance of ESTP, but I can't really see it).
Squidward: ISFP 1w9 (He's a pissed off artist that loves art and music that just won't be left alone to enjoy his passions. If he was an Si dominant he would have no problem with day to day routine, which he appears to greatly dislike).
Krabs: ESTJ (I don't think this is disputed).
Sandy: ESTP 8w7 (I think this fits very well, she's a scientist who loves physical activity).
Plankton: INTJ 3w4 (Definitely Tert Fi over Inferior Fi).
Gary: xxTP (Gary isn't really typable as he doesn't talk. That said, his actions and attitude emit strong vibes of Ti).