A little background first. On November 23, 2005, Bandai released the Japanese Tamagotchi model called the EnTama. The English-language model Connection V4 is somewhat similar to the EnTama. On July 22, 2006, Bandai released the Japanese Tamagotchi model called the UraTama. Compared to the EnTama, the UraTama is very similar, except the characters are very strange versions of those on the EnTama. The English-language model Connection v4.5 is somewhat similar to the UraTama.
"Ura" generally means the other side / the dark side / the opposite side / the back side. In the case of the UraTama, "Ura" means the inside. The EnTama characters live on the surface of Tamagotchi Planet. UraTama characters live inside Tamagotchi Planet. In the opening scene of an UraTama character's visit to the UraTama Town web page, you can see her/him going into Tamagotchi Planet's mouth.
Compared to their EnTama (& V4) counter-parts, UraTama (& V4.5) characters may have wings, tails, or horns.