Old Friend

Someone knocks on the door of your overly spacious apartment. It's an Old Friend from childhood, or an old college roommate -- someone you knew long ago but lost touch with. Maybe he just stopped to say hi, or maybe he needs to bunk down at your place, or maybe he wants to share a holiday with you. He is more wild and crazy than you. You may be reluctant to join his hijinks at first, but now that he's around, you start joining in.

This can be the premise of a work or a series. Think The Odd Couple or Supernatural.

If the Old Friend messing with your life isn't part of the premise, then Status Quo Is God will eventually have your friend leave, or you give him the boot. You will likely be unhappy; there's more than even odds he will be, too. The visit of the Old Friend will leave you wondering how little he's changed and how much you have. Or, on occasion, vice versa.

In sufficiently recent works, the Old Friend is likely to be a New Age Retro Hippie.

Compare Beleaguered Childhood Friend. Not to be confused with I Want You to Meet An Old Friend of Mine, but can overlap. Contrast Old Flame Fizzle, discovering that the friendship (instead of the love) is gone.

Anime and Manga

 * Parodied on Sayonara Zetsubo Sensei with a character in love with all things old-fashioned who claims to be an old friend of the title character's..

Film

 * A darker example occurs in The Third Man -- the main character, Holly Martins, goes to post-WWII Vienna to meet up with an old friend, who.
 * In Kiss Kiss Bang Bang, Harry is reunited with childhood friend/crush Harmony at a Christmas party. True to this trope, her appearance heralds a whole lot of trouble for Harry.

Literature

 * In Dan Abnett's Gaunts Ghosts novel Blood Pact, an old friend of Gaunt's from school is a major character -- although it is inverted, with Gaunt turning his life upside down.

Live Action Television
"Spence: You didn't tell me you were on call...Hey, you know, I have a presentation to give tomorrow. Ask me if I want to go out drinking tonight.
 * Scrubs uses this a lot:
 * J.D. and Turk's old college buddy Spence, played by Ryan Reynolds, comes to visit. They envy Spence because he gets paid more money, works fewer hours and gets to drink in his time off. His whole purpose in the episode is to take them out and encourage them to party like the old days; they drink while on call and then have to deal with the consequences.
 * Spence even gets a What the Hell, Hero? moment when they tell him about the verbal thrashing they went through from Cox the next day.

Turk and J.D.: (sheepish murmuring)

Spence: No. I have a presentation."


 * Turk's brother Kevin turns up, constantly trying to be a bundle of fun and energy to mask up his unhappiness with his divorce. He drags Turk out with him, making Turk realize that he needs to make time for his brother, even if his wackiness is annoying, because Kevin needs the emotional support. Doing so, however, causes problems in Turk's relationship with his girlfriend Carla, so actually Turk would have been better off saying no to Kevin.
 * J.D.'s older brother Dan shows up in several episodes. His lack of maturity and responsibility in comparison to his younger brother is highlighted in a variety of ways, though each brother usually ends up learning something from the other by the end of each of Dan's appearances.
 * Elliot's sorority sister Melody comes to visit. She still acts as wild as she did when the two were in college together, and this is contrasted with how much Elliot feels she has changed over the years.
 * Friends has "Gandalf" (because he's the Party Wizard) who is never seen but is described as exactly having this effect. When he fails to get into town for a planned weekend of fun, the guys try to replicate the results without him and find they can't because they've grown up and their tastes have changed.
 * Green Acres used this trope when Lisa had relatives visit. In one episode, her mother came and the entire town turned out to welcome her.
 * One episode of How I Met Your Mother is dedicated to the phenomenon of "Revertigo", whereby meeting an old friend temporarily turns you into the kind of person you were when you knew them. Truth in Television, of course.
 * Done repeatedly on all the CSI series. Usually one offs, but Sam Braun recurred and was revealed as Catherine's dad.

Western Animation

 * In an episode of Daria, Jake and Helen's old hippie friends come stay with them for a weekend. The friends are still living the hippie lifestyles, and at first Jake and Helen try to rekindle with their hippie roots. But eventually their friends reveal how weary they are of the hippie life and instead decide to adopt a more modern lifestyle.