CEO Johan Pilestedt said the side-scrolling multiplayer action game learned from each title's approach to customisation and balancing.
"What is the key thing that made GoldenEye... so successful?" he told Digital Spy.
"In one corner of that is the fact that you could customise your games in the way you could. And that is similar to Smash Bros as well.
"You can customise your game in any way you like, you can choose characters even though their effect on gameplay isn't that big, but at least you get to communicate who you are with those characters.
"That's something we took with us with Showdown. The characters do play an important role, but we didn't want to make them that unique."
Gallery: View images of The Showdown Effect:
Copyright: Paradox InteractivePilestedt continued: "We didn't want to have health point differences or anything like that; we wanted characters to be mainly cosmetic, but with one additional item that changed play style.
"If you had two or three items, that would mean you would get a bonus or a drawback or something, then people probably couldn't tailor their character in a way they otherwise would."
Paradox Interactive said last week that it would publish on the new Xbox and PlayStation 4 if they were more open platforms.
The publisher also revealed Brian Blessed DLC for War of the Roses, a beta for The Showdown Effect and a new expansion for Crusader Kings 2 at the convention.
It will also make its debut on tablets with the release of Magicka and Leviathan Warships later this year.
The Showdown Effect will be available from March 5 on PC for £7.99 / $9.99.
> Read our hands-on preview with The Showdown Effect
Watch a trailer for The Showdown Effect below: