Series symbol

A series symbol is a distinctive iconography that represents an in-game universe in the Super Smash Bros. series and that is also present in Super Smash Flash 2. These symbols are assigned to playable characters, stages and, to an extent, items. Within the game, the symbol can be seen next to a character's damage counter, taking on the same color of the player's number. It can also be seen behind the character's portrait on the character selection screen, next to the stage's name display on the stage selection screen, in the Vs. screen of Classic mode, and in the background for personal Target Smash levels. Pages on the Smash Flash DOJO!!! also carry a symbol on the upper left corner of the update. Despite being a simplistic feature, there were no symbols in the original Super Smash Flash.

List of series symbols
Below is a list that compiles and explains each symbol's source origin:

Minor symbols
There are no specific universes assigned to these symbols, but nonetheless, they receive the same treatment as main symbols.

Former symbols
These symbols were present at some point before being discarded due to updated symbols.

Trivia

 * As a result of their early implementation into the Super Smash Flash series before their eventual inclusion into the Super Smash Bros. series, FINAL FANTASY and Castlevania are currently the only universes to have quite different symbols from the ones they have in the official titles (the series' initials "FF" and the silhouette of a bat and Dracula's Castle, respectively). Any plans to update the symbols (as was the case for Mega Man) by developers are unknown.
 * Likewise, Metal Gear was also given a new symbol in Super Smash Bros. Ultimate—an exclamation mark—replacing the old FOX Unit's insignia/Kojima Productions logo.