The Soul series games generally take themselves seriously, but there are moments. For instance, in III's character profile, Sophitia and Cassandra have "Weight" filled in as "Unknown (refuses to reveal)" and "Has lost weight recently" respectively.
Yun-seong's "good" ending in Soulcalibur III. He chooses steamed buns over Soul Edge, and they turn out to be bait set up by Mi-na so she can knock him out and bring him home.
Cassandra's ending in Soulcalibur III. Either the sword is broken forever or poor Cassandra has to fix the sword alone as punishment for breaking it. This despite the fact that she just destroyed Soul Edge.
When you bump into Xiba, Leixia, Natsu, and Maxi as Patroklos in SCV's story mode. Patroklos needs a favor from the group, Leixia and Xiba in particular. Both agree but Leixia slyly responds that "nothing is for free" in a way that feels like she's flirting with Patroklos. Xiba's thought on the situation? "Hey, he can buy us dinner!"
And Leixia's automatic "No, you idiot!" had this Troper howling.
Both of Olcadan's endings in III are hilarious:
Ending 1: Opens his own school of martial arts and beats the ever-loving crap out of a few of his students who try a sneak attack on him.
In SCV, the cast now has Ring Out-specific lines. Ringing out Raphael makes him yell "HAVE YOU NO SHAME?!?" If you do it again, he yells "DO YOU KNOW NOTHING ELSE?!?"
Other characters have great ring out lines as well, such as Natsu going "AW, HELL!", or a player-created male character with the "veteran knight" voice set yelling "I CAN'T LOSE!" during the first and "IT'S STILL TOO SOON!" during the second time.
There's also the custom voice that yells "I'M TOO YOUNG TO DIE!!"
Kilik gets "I FORGOT OF SUCH METHODS!"
Edge Master is quite sporting about the matter: "GOOD STRATEGY!!" "NICE AIM!!"
Alpha Patroklos, on the other hand... "DAMMIT!" "STUPID!"
Some of the character designs you can encounter in Quick Battle are pretty funny. One of the ones that stands out is the person you face to earn the Drunkard title. Everything about him, his name, his design, and his fighting style all seem like they were legitimately designed by someone who was drunk off their ass.
This one's meta, but Ezio's backstory in SCV is that he was "dimension warped" over during a Time Jump portion of Assassin's Creed: Brotherhood (the Soul series is set over a century after his own death in 1524); the thing is that based on the lore in question (fleshed out in the Brotherhood novelization) and on the narration of Shaun Hasting (in 2012) mentioning the events (though dismissing them as an Animus glitch), this may well be canon in the Assassin's Creed universe!