Téa Gardner, who appears in both the franchise and abridge series, is a strong advocate of this belief (though exaggerated far more in the abridged series).
Téa: Nothing can destroy friendship. It's the most powerful force in the universe. It's even stronger than Chuck Norris!
Téa: Screw medical science. I'm talking about friendship.
Doctor: I beg your pardon?
Téa: Friendship is the only cure for a lighting bolt to the head.
Yami: That's right. Joey was struck by lighting and with the power of friendship, he's okay.
Joey: Yep, my brain be thinking good and stuff.