It takes a while, but in the end Sam's daydreamy nature saves Finn's life. The blond behemoth pauses half way through undressing for no apparent reason. He just stands there for a minute, sniffing his pits and giving his body a pleased appraisal with his eyes.
And then, Sam looks down. He sees the tiny man between his bare feet but doesn't understand what he's looking at, not until he's crouching down and gazing with his mouth slack at the tiny creature who used to be his best friend and, before that, greatest competitor. "Whoah... What happened to you?" Sam asks, in a kind of awe.
From Finn's perspective, the giant's prying eyes are a little overwhelming. It's like Sam's huge face is descending from the sky, filling his entire vision. The boy's voice is so loud and deep at this proximity, he feels the vibrations in his bones. "I need help, dude! I need you to get me into some kind of secure box and then find a doctor!" He screams each word as clearly and loudly as he can, knowing how easily Sam can be confused. Right now his whole future is riding on this big muscle boy.
...And from where he stands, that future doesn't look promising.
Sam's fingers descend on him, aiming carefully and then clamping around his arm and yanking him in the air. "HA HA HA. OH MAN." Sam laughs like a big kid, swinging a screaming little Finn in the air. "LOOK AT YOU! YOU'RE SO ITTY BITTY!" The blond boy chuckles, now taking it upon himself to roll Finn in between his meaty palms, feeling his tiny delicate roll and tumble. "I CAN'T BELIEVE I USED TO COMPETE WITH YOU FOR GIRLS, AND POPULARITY, AND RESPECT. YOU'RE JUST A LITTLE BUG!" He laughs in pure pleasure, tossing Finn into the air and catching him just to show off how easy it is.
When Finn gets a chance, he shouts breathlessly from the brute's fist, "Sam, I was your best friend! I thought you had my back!"
This affects Sam at least a little bit. He tilts his head sympathetically, still smiling. "Aww, don't take it personally, dude. A guy only gets a chance like this once in a lifetime. Not only to be top dog at this school, but to have my own little pet man to remind me of how god-like I am with your puny little ass." He chuckles, tossing Finn in the air again.
Now that Finn has been officially demoted from best friend to squeaky little pet...