When your favorite show gets canceled it can feel like it's disappearing forever, but sometimes the ghost of a show lives on in its actors. Sometimes the cast of one show reunites on another, and even though they're all different characters in a different world they still reference their shared history outside the show's universe. Here are some of the best examples:

1. Parks and Recreation references The West Wing

On the Parks and Recreation episode "Live Ammo," Bradley Whitford guest stars and reunites with former West Wing cast member Rob Lowe. Their characters in The West Wing, Josh Lyman and Sam Seaborn, worked together as senior staff under President Bartlett. Though they're still working in the government in Parks and Recreation, they seem to have been massively demoted to Pawnee. Whitford plays Councilman Pillner and while he's never in the same room at Chris Traeger (Lowe), the writers at Parks don't forget to throw in a little tribute to The West Wing.

2. Raising Hope reunites the cast of My Name is Earl

Greg Garcia obviously did not deal well with the cancelation of his show My Name is Earl, even though his new show Raising Hope was picked up shortly thereafter. Actors from Earl made continual appearances on Raising Hope, culminating into a full-fledged reunion in the episode "Making the Band." The episode is so lousy with references that one clip cannot encompass them all… but here is one clip anyway.

3. Cougar Town reunites the cast of Scrubs

Similar to Garcia, Bill Lawrence seems to have a big ol' spot in his heart for past shows. I guess it's not a surprise that Lawrence misses the glitz of having a moderately successful show like Scrubs, compared to his underwhelmingly successful Cougar Town. In an attempt to keep Cougar Town from being scrapped, Lawrence threw a hail mary pass by grabbing some of the recognizable faces from Scrubs and moving them from the hospital to Florida (which isn't that different considering the number of geriatrics. Ba-dum ching.)

4. Arrested Development references the history of Happy Days

It can be argued that no show broke the fourth wall as well, or as frequently, as Arrested Development. Henry Winkler had a recurring role on the show as the Bluth family's inept lawyer, Barry Zuckerkorn. This made for a Happy Days reunion between himself and Ron Howard, the show's narrator and producer. Allusions to the Fonz were peppered throughout the show, but the best example comes when Scott Baio, known for his role as Chachi, appears on the show as another terrible lawyer, Bob Loblaw. Loblaw replaces Zuckerkorn as the family lawyer, mirroring the same way Scott Baio replaced Henry Winkler as the cool hearthrob in season 5 of Happy Days.

5. Up All Night references Arrested Development

Arrested Development strikes again in Will Arnett's new (now old) series Up All Night. Tony Hale guest stars for an episode; the two played brothers on AD and lucky for us, Hale/Buster/Flirty Doctor utters his go-to line.

8 Times TV Shows Slyly Referenced Actors Earlier Roles - Image 12

6. Psych pays homage to Twin Peaks

Back in 1990, David Lynch created the series Twin Peaks. Canceled after the second season due to low ratings and probably confused viewers, the show has become a cult favorite. The current show Psych brought back three former Twin Peaks stars in its episode "Dual Spires:" Lenny Von Dohlen, the agoraphobe, Sherilyn Fenn who played the odd, goth classmate and Sheryl Lee, Laura Palmer herself. Twin Peaks fans should really watch the whole episode to see all references littered through the episode, but for the lazy among us, here are some of the best images.

 - Image 1

This Psych character is an anagram for Twin Peaks character Laura Palmer.

8 Times TV Shows Slyly Referenced Actors Earlier Roles - Image 12
8 Times TV Shows Slyly Referenced Actors Earlier Roles - Image 12

7. Last Man Standing Reunites Father and Son from Home Improvement

Beloved sitcom actor, Santa Claus, and convicted felon Tim Allen was made famous from his popular ABC show Home Improvement. He recently reentered the world of TV sitcoms (and annoying commercials) with the show Last Man Standing. The struggling show tried to boost its ratings by staging a mini- Home Improvement reunion, getting Tim Allen and his TV son Jonathan Taylor Thomas back together. While their references aren't exactly subtle, I'm sure audiences were still excited.