You're wrong, the secret ingredient is Patrick Source.

Crabs can regrow limbs.

They've got it all wrong. Just like cow patties, crabby patties do not contain meat.

The Krusty Krab is a crab trap

There is an episode where he tries it and says something that basically hints that he just ate himself and didn't think it was bad.

You May Live To See Crab-Made Horrors Beyond Your Comprehension

I thought it was whalefall.

Actually Hillenburg said in life the Krabby Patts dont have meat of any kind

Alex Bale (the spongebob theory guy) suggests it's whale meat...

https://www.youtube.com/watch?v=NlCb3ZNalqA

Enjoy this rabbit hole! It's a wild, riveting ride.

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Kelp is seaweed.