None really. I made it up lol. But anyways, if there were such a thing as 4th and 5th party characters, here's how I'd interpret it:
3rd party- Non-Nintendo VG character (Sonic
, Snake, MEGAAAA MAN, Pac-Man, *duh nuh nuh nuh nuh nunnn nuh nuh nuhhhnn* GENOOO, Bomberman)
4th party- Fictional non-VG character (Goku, Jessie and James from Team Rocket)
5th party- Real-life people (Sakurai- the creator of Smash Bros)
6th party- High-ranking officials (Obama)
7th- Deities (God, Jesus, Chuck Norris, Bruce Lee, Gary Oak)
Actually Jessie and James (and their first generation Pokémon) do appear in Pokémon Yellow Version. Thus, they are 1st party... I think... kinda. Well, then again they are based off the anime and manga, so you're right; although, they are owned by Nintendo...
Also, 4th Party party gaming companies are rival companies with rival companies. So that would be Sony and Microsoft's 1st and 2nd party games, characters, and franchises.
5th Party would be other fictional characters from other medias that aren't owned by Nintendo. These include the likes of Goku, Naruto, that 70 year old woman in that soap opera your mom watches who's been on their for 53 years and still thinks she is 17, or Michael Scott. (I had to reference that show! >.>)
6th Party would be people on television, radio, etc would pretend to be real, but aren't. Think reality TV, all those crappy TV judges, any dumb show about anything from New Jersey, anything on Maury or Jerry Springer, etc.
7th Party would be real people like your mom, the man who is currently making out with your mom (or as the inner redneck in me would say, "hey! that's mah brothah!"), and even YOU!!!!
8th Party would be the high ranking officials, like President Obama, any President or Prime Minister, any dictator, or your local money launderer you call a Senator.
9th Party would be deities, mythological creatures, God, gods, or immortal entities. Zeus, Jesus, ever major figure from the French revolution (they were worshiped as deities! XD), etc would be in this category.
10th Party would be America.
11th Party would be Masahiro Sakurai.
12th Party is Andross.
13th Party doesn't exist because it's bad luck.
14th Party is Andross' BRAINN!!!
15th Party is Shigeru Miyamoto.
16th Party is a lie.
17th Party is a government conspiracy.
18th Party is illegal.
19th Party is "Why wasn't Waluigi in Brawl?" conspiracy theories. Because the government, IRS, Nintendo assassins, Japanese ninja wars, Chinese gangsters, and bunny rabbits are totally the reason he didn't make it!