Anticlimactic Parent

Anticlimactic Parent is a version of The Reveal where a character spends the episode getting the cast in an uproar about a parental visit. This usually because the parent is said to have the character traits they lack, and he wants to make a good impression on them. After scrambling to make a complicated deception, a few things can happen:

The parent's reputation was exaggerated, and they get along fine with everyone, except the child.
The parent has mellowed down over the years, and becomes a humorous rather than antagonistic Foil.
The parent really is as bad as we're told, but the visit goes off well thanks to someone who wasn't in on the plan.

Examples of Anticlimactic Parent include:

Anime and Manga

Keroro Gunsou's father causes quite a scramble, until he leaves much sooner than expected when the weather doesn't agree with him.
Please Teacher! has Mizuho worry what her family will say about her being married to a student. Her mother Hatsuho has no complaints, though slyly implies to the reader both of them show an interest in younger men. (This also works as a slight lampshading of the show premise, suggesting Mizuho isn't entirely inconvenienced by her situation.)
In Fruits Basket, so many people in the Honda family were against Katsuya and Kyoko's marriage that Kyoko wound up psyching herself up to think that Katsuya's father (who he used to be at odds with) would be the worst of the lot. He winds up being the only family member who happily approves of them, and eventually the only one willing to take in their daughter Tohru once both her parents have died.
- When Arisa first meets Tohru she's a gang member who admires Tohru's mother who was once a ruthless gang leader. She goes to Tohru's home to visit her and finds out she's a devoted and loving mother. As she says in the flashback: "The Kyoko-san I had looked up to had developed a total mother complex." After spending time with the family Arisa leaves the gang, is rescued from them beating her up by Kyoko and returns to school.

Literature

The book A Little Ray of Sunshine is based on this. Emmy's mother is a Maternally Challenged Evil Matriarch, and each chapter starts with various heartless quotes from her mother over the years. But by the time we meet Lily, she's undergone a massive personality makeover.
In Harry Potter, Mrs. Weasley has the whole family scrub the house for the arrival of Fleur's parents, apparently based on the logic that they will be as critical as Fleur is. Instead they turn out to be incredibly jovial.
In Everworld, Senna goes to meet her mother in Everworld-Egypt fully expecting her to be an all-powerful witch who may well choose to smack the crap out of her. Instead she discovers that her mother is little more than a sycophantic servant of the Amazons and nowhere near the intelligent villainess that her daughter grew up to be. If anything, Senna seems angry that she was abandoned for a life that wound up being so pointless.
In Percy Jackson, Percy naturally assumed from the way Annabeth talked about her father and stepmother that they treated her badly. When he came to visit her home, they were friendly and helpful.

Live-Action TV

Kamen Rider Ryuki did an episode of this.
In the Robin Hood spoof Maid Marian and Her Merry Men, Marian never admitted to her mother that she was an outlaw. This leads the main characters to keep up the charade of being The Merry Dentists. However, when Marian is captured, her mum leads the rescue effort and ultimately reveals she has her own geriatric gang of outlaws.
In Power Rangers SPD, the doofus character Boom flunked out of the academy in three days but told his parents he was the heroic Orange Ranger. Hilarity ensues when his parents visit and learn the truth.
There was a version of this in Will and Grace where Jack envisioned his stepdad as cold, unloving, and ubermacho. When the gang visited him, he was a friendly guy who got along very well with Jack's son.
- Jack's very straight son.
- Also on Will and Grace, Will was trying to protect his presumably gay nephew from criticism by this mother (the child's grandmother) over wanting to stage a play for the family. But the mother had mellowed, attributing it to the experience she had gained raising Will.
On Chuck, Ellie spent the Thanksgiving episode stressing out over the arrival of the Awesomes (her fiance's parents), only to have them not show up at all. Then they show up in the next episode, where they mainly get on her nerves for taking over her wedding planning.
Blackadder has to impress his ultra-puritan Aunt and Uncle at a dinner party so he can earn his inheritance (a stunning feat considering his Aunt and Uncle consider things like chairs and mashed turnips "too decadent") in the end, his uncle breaks his vows of silence and tells Edmund that he had a wonderful time. then everyone gets really drunk
On Spaced, Brian's mother visits and he spends the whole episode pretending to be a lawyer, only to discover that she'd always wished he was an artist. Then he gets to reveal to her that he actually is!
In an episode of The Monkees, Davy's grandfather is flying in from England for a visit, under the impression that Davy is a big star. Panicked, Davy convinces the rest of the band to pose as his chauffer, houseboy, and personal chef to keep up appearances. Of course, given what show we're talking about, it fails, but the grandfather allows him to stay (rather than taking him back to England) because he has "such loyal friends".
In an episode of Friends, Ross is dreading a visit from Rachel's father. It starts out as badly as he feared, but they soon find common ground criticizing Rachel.
How I Met Your Mother: After a ton of build up over the revelation of Barney's father, it turns out his father is...a regular old family man (though he is played by John Lithgow at least). It's seemingly subverted at first when Jerome (Barney's father) tells him all these awesome things about his life, like being a manager for a band, and being just as much of a sexual deviant as Barney himself, but it's later revealed that Jerome made it all up just to impress Barney, who was having a hard time accepting that Jerome wasn't the most legen...wait for it...dary daddy ever.

Theatre

The Boys Next Door has an example of this when Barry's father comes to visit. The father is really scary, actually, and only seems to bring out Barry's neuroses.

Video Games

In Psychonauts, Raz spends the entire game complaining about his father, and how he won't let him be a psychic due to an old family curse. Raz even ends up battling his own mind's demonic version of his father. This trope occurs when Raz's father uses his psychic powers to enter Raz's own mind to save him, and is genuinely saddened by the way his son views him.
- He's a little confused, too-I mean the guy has forest green skin and his outfit looks more like a freakish tattoo than clothing. Whatever your intentions were, you must have seriously sent the wrong messages when your son's mental image of you is that far off.

Web Comics

Ozy and Millie plays with this when introducing Ozy's adoptive father Llewellyn. Ozy states matter-of-factly that his father is a dragon, and until Parent-Teacher Day, Millie freaks out that her best friend is merely being raised to be snack food for a demonic monster from beyond her (already pretty wild) imagination. On meeting him, she is, along with her mother, immediately charmed by Llewellyn, who becomes one of the strip's iconic and most charming characters—oh, and is completely harmless (aside from the fire-breathing thing).
- Even the fire breath is pretty harmless. Which is to say it doesn't have to be, but it's never been used in anger (an emotion Llewellyn seems incapable of feeling to begin with).
Marena from Keychain of Creation initially describes her mother as a manipulative Evil Matriarch. When Sonorous Aria actually shows up, though...

Aria: Petal!

- Partial subversion in that she is a Manipulative Bastard, just an Affably Evil one.

Western Animation

The Dexter's Laboratory subcartoon Justice Friends has Major Glory making his friends scramble to impress his jingoistic Uncle Sam, only to discover his uncle has mellowed into a hippie to avoid high blood pressure.
In My Little Pony: Friendship Is Magic Twilight, and by extension everyone else in town, tend to over-prepare for Princess Celestia's appearances. In line with this trope, she generally is appreciative of the efforts, but actually enjoys a casual visit much more. In the first season's finale, she lets her own palace get wrecked specifically to avoid the standard boring gala.
An episode of Kappa Mikey uses a distant permutation of this.. Mikey lies to a reporter about his life in Tokyo, then forces his castmates into an elaborate ruse to fool his parents when they come to visit after reading the article, making them cancel a vacation at the beach for a visit that, ultimately, never comes: killer bees force the airport to close, and Mikey then decides, rather than coming clean, to go find stand-ins for his parents and fake the visit. Needless to say, everything falls apart in utterly ridiculous ways.
In SpongeBob SquarePants, Patrick Star is in a panic because his parents are due for a visit. Because they constantly belittle him for being an idiot, Spongebob volunteers to pretend to be even dumber than Pat. This works well until all three begin to ridicule Spongebob and he storms off. Only then do Patrick's "parents" realize that they're complete strangers: "Oh, that's right. We don't have a son!" Patrick's real parents arrive, and are just as stupid as their son, if not more so.