Dude...Sorry, I have alot on my plate, so I will finish...
"The captain looked into his folder again, and said lets go question Spongebob, I dont think he did it...lets eliminate him as a suspect first."
Later at the Pineapple
"Spongebob, I must see the peanut flavored mayonaise you made." Said Mermaid Man.
"Anything for you Mermaid Man..." Said Spongebob as he pulled out a HUGE Jar of peanut flavored mayonaise. "here it is."
MM looked at the jar for a long while, and noticed that there were onion bits in it as well. "This isnt the Mayonaise that killed Fred!" Proclaimed MM.
"So it was Old Man Jenkins!" said Barnacle Boy.
Later at OMJ's house!
Old man Jenkins bursts out the back door, and MM&BB, and all the cops follow behind him. Finally they catch him, and arrest him.
"Why did you do it old man!?" asked BB
"I did it to keep him quiet! He was gonna sell my formula for peanut flavored mayonaise to Plankton, and he was going to make millions! I couldnt let him do that, so I force fed Fred a gallon of my special mayonaise, I had no idea he would die! I swear!"
After a lengthy trial OMJ was set free because he was too old to put into prison, he now lives at Shady Shoals under constant police surveilance.
MM&BB went back into retirement, but with OMJ living at Shady Shoals, they moved back to the Merma-Lair.
Spongebob went back to being well...Spongebob.
And they all lived happily...errr insanily ever after!