Pretty self-explanatory.
However for Spike, Tournament Grinder:
"all of you who are falling over themselves to play with Spike, please remember that Rule 13 exists, and she only functions under whatever rules the rest of your playgroup sets for her. "
And also for Johnny, Combo Player:
"[He is] likely to give your playgroup a headache or lead to problematic games if you're not careful. Use responsibly and remember that if you're playing cards your opponents don't enjoy playing against, they probably won't want to play with you any more."