Gideon, a wandering vagabond from The War for the City of Peace Campaign. The PCs first encountered Gideon on a stormy night while staying at an Inn. They thought he was just an eccentric beggar, bearing only the clothes on his back, a backpack, quarterstaff, and numerous charms dangling from his neck, who often hums to himself.
It was fun playing the humming part. Because every time the PCs would ask, "what are you humming?" He'd say, "humming? I'm not humming."
He even came with his own theme music when he first met the PCs (Just listen to the music--ignore the horse playing soccer).
That's "Concerto in C Major for Sopranino Recorder" by Karl Stangenberg on 99 Darkest Pieces of Classical Music.
The PCs hired Gideon as a guide to lead them through some unknown territory on a quest to find "The Miracle Hermit."
Little did the PCs know that Gideon had actually sought them out, after hearing about their dealings with the arch-villain of the campaign. He knew the villain's backstory, but first wanted to see if the characters were who they said they were.
Gideon had the powers of both a druid and a bard, but I never statted him up. There wasn't any need. The PCs thought he was a low-level nobody, so they protected him from combat. They even told him he should leave the group when they when to assault an evil temple. Gideon, a bit annoyed, left.
The PCs forgot all about him until an adventure or two later in the campaign, when the finally were going to track down the main villain. The player who took copious notes remembered something Gideon had said offhand. Everybody else went, "huh? Who's Gideon?"
"We have to find him! He knows something."
And so they spent a session tracking down Gideon.
So, if you're ever a player in my campaign, you should pay attention whenever an NPC enters with his own theme music.