Your regular fish tomato

Fish Tomato is a type of tomato that looks like a perfectly normal tomato, but tastes like fish. Such specimens are extremely rare, although there is not much demand for them anyway.

(In)famously, fish tomatoes are liked by Bart Hufnagel. He also claims that he grows them on trees, although it is undisputed that tomato plants are vines. This became the core claim of Hufnagel's Fish Tomato Hustle.

It is not exactly known what makes a tomato taste like fish. Several hypotheses advanced by scientists are published in paid scientific journals, and are enthusiastically ignored by the public.

The more approachable version was suggested by John from a pub across the street, who theorized that fish tomato is a rare mutation that develops an actual miniature fish inside. When his buddy Charlie disputed the conjecture, arguing that it is “impossible”, John begged to differ and supplied a drawing:

A schematic of John's hypothesis