[[WMG: Annie the Mermaid from the video game sequel is, in fact, Sloth.]]
Some randomly visiting deity; possibly LightNovel/HaruhiSuzumiya, figured that there needed to be a love interest in the story; and that Sloth was the wrong gender and kinda ugly. One [[RealityWarper POOF]] later, and ta-dah!
* Or maybe the [[Franchise/TheHitchhikersGuideToTheGalaxy Heart of Gold was passing buy, and it was JUST that improbable.]]
[[WMG: Mikey seems to know more about One-Eyed Willy than he's telling.]]
Mikey tells One-Eyed Willy he's the "first Goonie". Could it mean One-Eyed Willy is his ancestor? Was the surviving pirate who escaped the massacre with the map and the doubloon Willy's son?
[[WMG: Mikey is the reincarnation of One-Eyed Willy]]
An elaboration of the above theory; he seems to have an almost intuitive knowledge of One-Eyed Willy's treasure: he is able to find what professional treasure hunters couldn't, he successfully avoids the traps (especially the final one), and he even has a similar love of Rube Goldberg-esque devices.
* In the novelization, Mikey (who's narrating the story) idly speculates that he is either the descendant or the reincarnation of Willy.
[[WMG: Chester Copperpot is Mikey's grandfather or other relative]]
Chester Copperpot was one of the only people to know about the treasure and look for it (even though he failed). Mikey finds a map and a metal or stone key in his attic. These items, but especially the skull-shaped key, are probably the only ones of their kind, so in order for Copperpot to get as far as he did, he would have needed at least the map. However, he didn't bring the map with him because he either memorized it (he was a dedicated old coot) or he found the shortcut through the well. Mikey has the map and the key because Copperpot is his ancestor, and his dad inherited it when Chester never came back. This would also explain the newspaper article in the attic.
* Though he couldn't be his paternal grandfather, since his last name obviously isn't Copperpot. Its very unlikely that's Mikey's mother's maiden name, because its not a very common surname, unless his mother's side of the family changed his name. On the other hand, Mikey's dad was probably an only child and didn't even know Chester was his dad.
* Correction: Mikey finds the map and a doubloon in his attic. The doubloon has holes punched in it that line up with landmarks to indicate the right place to start following the map's instructions. He finds a bronze key ''on Chester Copperpot's corpse''.
* It is explicitly stated that Mikey's father was the assistant curator at the local historical museum and the stuff in his attic was the leftover material from an exhibit on the history of Astoria, not their personal belongings.
[[WMG: The treasure map clues conveniently rhyme in English because they were written in English]]
The ConvenientlyPreciseTranslation is possible because One-Eyed Willy (not exactly a Spanish-sounding name) wrote the clues in English originally, and then translated them into Spanish as an extra layer of obfuscation. Discovering that the English translation can easily be made to rhyme is a clue to the person using the map that they have the correct wording.
* I call this canon. It makes sense as yet one more way Willy was able to mislead and fool anyone searching for the treasure, and it also fits both his name not being Spanish (unless Willy were a translation of a diminutive for the Spanish version of William) and the fact that few Spanish pirates would have been plying the waters off Astoria. (If anywhere, they would have been down near Los Angeles or Mexico.) As to how he knew Spanish--interaction with said Spanish pirates, and the Spanish authorities in California. The intelligence required to build his devices already shows him to be a well-educated man (and a number of pirates were).
[[WMG: One-eyed Willy had that name ''long'' before losing an eye.]]
Not that they'd mention or know it in the move, if you know what I mean.
* He didn't lose an eye, he literally did not have one. He had no left eye socket either.
[[WMG: ''Film/TheMonsterSquad'' is a SpiritualSequel.]]
[[WMG: The sequel will never be made.]]
[[WMG: Goonies and Gremlins share a universe.]]
Chunk wasn't lying, Gremlins were attacking the Goon Docks, but the Goonies were able to contain it pretty quicly