Jeto has a hidden 3rd level,
Jayzel was supposed to be a drag queen,
Baba was supposed to be a skinny bishonen,
Magenta's description was slightly changed (sex object -> slave),
Orlok's ability was supposed to be Defeat : Poison
and Galen's ability used to work in level 1 & 2.

...That's all I know.

This one is a bit farfetched but still funny. The maximum amount of attack a character can have is 273. I'll explain why:

Have a hand consisting of Trey, Trey, Ambre and Sting (or any other 10 powered card). After both Treys have gained 4 pillz (without using any themselves), you should have 20 pillz + 1 free pill. Attack with Sting on a Courage round and 21 pillz times 13 power equals 273 attack.

If anyone can prove me wrong, please do! I know that there are 11 powered cards but they all need either bonus or support which wouldn't fit in this hand.

Arawaka and Jaxx Ld has the 666 number
Arawaka 6 power and -6 opp life min 6
while Jaxx Ld is 6/6 with -6 opp attack min 6

The Urban Rivals Wiki has a lot of Trivia on most cards http://urban-rivals.wikia.com/wiki/Urban_Rivals_Wiki.

Dolores Boss has 3 alternate full arts
http://images3.wikia.nocookie.net/__cb20110412131648/urban-rivals/images/3/35/Dolores_Boss.jpg

Nakata's 2nd evolution, if I remember right, had the same pose... just different colored clothing

Vickie cr's art was altered, then changed back.

Before smokey went cr, he only cost between 2-3K

Arno cost less before the elo ban

Ratanah was elo banned so Shakra and Roots could stay playable. Now both are banned. Also they both cost about twice as much as before the elo bans.

Noels usually have abilities opposite of what the non noel's ability is. Gaia Noel isn't the opposite of her non noel counterpart, but the same ability and different stats.
Lola Noel is completely different to Lola.

Miss Jessie is the only miss clint city winner that isn't a 5*

And Zdrone had a 5* evolution, yup

Katan originally had different 1st level art before a game company told them it was too much like one of their characters.

@Tanto89: Don't forget Jody...

No one can beat robb at darts

If you scan market for salesprice of some card and see a card that has huge lot of cards for sale in the lower price range you might think "Oh geez, that will never rise" and sell your card cheaper than that lot.

In reality investors use this trick time to time to milk cheap card out of market, buy them in masses, then remove their big barrier and let the price rise for easy profits. It would be actuallty cut their expected gains if someone buys that whole lot in such situation, and they often pull their cards from the market if people start buying them too much.