I like to imagine each of the 3rd Party character getting into Smash going through Mario and them interacting their own special way.

Sonic: Was a little bit awkward between the two of them, like two people that were bitter enemies, but was welcomed with open arms later on.
Mega Man: Was brought in with a blanket over his shoulders by both Sonic and Mario.Like seeing your friend on the street, and offering them a place to stay for the night.
Pac Man: Was Met with open arms, like seeing his childhood hero right in front of him.
Ryu: Mega Man's distant relative, invited to make Mega Man feel more at home.
Snake: Just kinda showed up. Everyone was terrified of him at first, but he made himself at home and warmed up to him.

… Can you tell I really want to write Smash stories? I really love all of these characters. Even the ones I know nothing about, like Marth.

After Final Fantasy VI for the Super Nintendo (well, actually Super Mario RPG was their last Nintendo title), Square-Enix moved onto the PlayStation almost exclusively, only putting some of their other titles onto the Nintendo systems like remakes and Crystal Chronicles, and other spin-offs recently. That's pretty much what is being referenced, the main series Final Fantasy titles moving to PlayStation, PS2, PS3/360, and PS4/Xbox One.

The last panel is more or less that Cloud gets motion sickness, which is a thing he gets in the Final Fantasy VII series.