Spoilers: 2.20 AHBL2.
Disclaimer: I'm just playing with Eric Krippe's characters from Supernatural. No money being made, only my debts are my own (but you're quite welcome to those).
Dean Winchester hates Gloria Estafan, he especially hates it when she's singing Anything for You. If it comes on the jukebox he'll either go to the washroom until it's finished or leave whatever dive he's in.
It started two weeks after Sammy left for Stanford he'd been driving down the road flipping channels trying to get a decent signal when it came on. The words floated through him and he had to pull over as tears threatened to fall. Sammy had left without thinking about how it would affect him. What did his life mean now? His only reason for living was wrapped up in protecting and caring for his kid brother and that was gone leaving an empty hole he didn't know how to fill.
'Anything for youthough you're not here since you said we're through it seems like years time keeps draggin' on and on and forever's been and gone still i can't figure out what went wrong '
Even now with Sammy back riding shotgun he still can't listen to it because it brings back memories of when Sam walked out and never looked back. He already knew he'd do anything for Sam but to listen to someone else singing a song about doing the same for someone tore him apart.
i'd still do anything for you i'll play your game you hurt me through and through but you can have your way i can pretend each time i see you that i don't care and i don't need you and though you'll never see me cryin' you know inside i feel like dying
He never told Sam why he got grumpy if the song ever came on the radio, he just flipped channels or switched it off. If Sam ever wondered he always assumed that it was too chick-flick for his brother. It wasn't until after his brother sold his soul and Sam was left in a bar listening to the song while Dean disappeared to the washroom yet again that he realised that the words rang true for how they felt about each other.
and i'd do anything for you in spite of it all i've learned so much from you you made me strong but don't you ever think that i don't love you that for one minute i forgot you but sometimes things don't work out right and you just have to say goodbye
When Dean came back into the bar that night Sam tried to tell him he that understood and that it cut both ways. Dean wasn't sure whether to believe his brother after all Sam had left him more than once, he could never leave his kid brother and couldn't exist without him. Sam tried to convince his stubborn brother that he always needed him but didn't always know how survive in the life they led.
i hope you find someone to please you someone who'll care and never leave you but if that someone ever hurts you you just might need a friend to turn to and i'd do anything for you i'll give you up if that's what i should do to make you happy i can pretend each time i see you that i don't care and i don't need you
Dean had broken all his rules about bargains just to keep Sam at his side; yeah he'd truly done anything to keep his little brother. Now though he was going to leave his brother alone and unprotected and it was up to Sammy to do anything to stop that. What Dean didn't believe was that Sam had left for Stanford thinking he was doing the right thing for Dean and allowing him to have a life without feeling responsible for him.
and i'd do anything for you i'll give you up if that's what i should do to make you happy i can pretend each time i see you that i don't care and i don't need you things don't work out right and you just have to say goodbye
Now Sam had his own goal to do anything to save Dean and prove that they didn't have to say goodbye to each other yet. Yeah the song might talk about their need for each other but they were stronger and wouldn't let it end. He needed to show Dean how much he cared and that he couldn't keep pretending and neither should his older brother.
Sam has got good at recognising the first few bars and either re-tunes the radio or gets Dean out of the bar before Dean has time to realise that it's that song again. Dean might complain but Sam always has a plausible reason that makes Dean laugh at his weird brother.
Sam is equally sure that if he can protect Dean from a record he can find a way to break the deal without either of them losing. He'll find the loophole and prove to his brother that he'd do anything for him, except leave him alone again.