A poster of 7 circles with "Dragon Ball City" written under them can be seen just before Goku is lured into the alley.
An elderly villager and the Village Chief seem to know a lot about Nimbus Clouds and believe that they cannot be destroyed. However, it is later proven that they can when Tambourine uses a Mouth Energy Wave to destroy the same cloud for good.
The martial artist Goku defeats for money is identical to the martial artist Krillin defeated in the preliminaries of the 21st World Martial Arts Tournament. Coincidentally, Goku compares defeating him for prize money to be like when he competed in exactly the same tournament.