Fish custard was a dish enjoyed by the Eleventh Doctor shortly after his regeneration. Having tried and hated many foods offered by young Amelia Pond's kitchen, the Doctor found frozen fish fingers and custard. He enjoyed them together, dipping the fish fingers into the custard. Amelia took the Doctor's enjoyment of fish custard in stride, which he noted as a sign of her bravery.

When the Doctor rejoined Amy Pond as an adult, he realised it had been "fourteen years since fish custard." (TV: The Eleventh Hour)

Amy, as an adult, would later invoke this dish in order to convince the Doctor of her truthfulness, although she referred to it as "fish fingers and custard" (TV: The Impossible Astronaut). Later, a TARDIS voice interface that interacted with the Doctor in the form of Amelia also referenced "fish fingers and custard". (TV: Let's Kill Hitler) These incidents showed how much the Doctor and Amy saw the dish as a symbol of their friendship.

During the Year of the Slow Invasion, the Doctor and the adult Amy and Rory ate fish custard at least once together. The Doctor said that if he ran a restaurant, it would be all he would serve. He also implied that he had created Yorkshire pudding, comparing it to fish custard, "Pudding, yet savoury. Sound familiar?" Neither Amy nor Rory appeared to find the taste offensive (or they'd become accustomed to it). (TV: The Power of Three)

Behind the scenes

• Matt Smith initially claimed it was actually fish fingers and custard he was eating and that he found it "gorgeous."^[1] They fish fingers were actually coconut breaded cakes.^[2] (COMIC: DWA 161) Smith later ate genuine fish custard on the Christmas 2010 episode of The Graham Norton Show.
• Steven Moffat has commented on the phenomenon of Doctor Who fans eating fish custard. He claims that it has "taken over from any other breakfast snack." (CON: Out of Time)
• In the real world, "fish custard" means something different from its Doctor Who usage. Fish custard is a custard that is actually flavoured with, or contains, fish. It is therefore a savoury dish. In reality, the Doctor ate what would be better termed "fish fingers and custard" — but he himself called the dish "fish custard".
• In the days following the broadcast of The Eleventh Hour, many Doctor Who fans, including Charlie McDonnell, posted videos of themselves to YouTube ingesting fish custard, with varying responses.
  

Footnotes