Relish Patties (also known as Freaky Clone Jelly Relish Patties) are rare Patties that only appear at the very end of the episode "Planet of the Jellyfish."
Relish Patties look like regular Krabby Patties, except they have the green goop from the Evil Alien Jellyfish Overlord that SpongeBob and Sandy defeated. Patrick came up with the idea after Mr. Krabs was thinking on what to do with the green slop, so Patrick then ate some of it and came up with the name. Mr. Krabs then sold them for four dollars more than a regular Krabby Patty. The Relish Patty might never have a different color other than green because of the goops' color.