Bob has a crush on Alice, Alice loves to sing, and Alice asks Bob's opinion. It turns out Alice is Hollywood Tone Deaf, but Bob doesn't want to hurt Alice's feelings and tells her that she's the greatest. This Idiot Plot continues, because apparently constructive criticism does not exist in this universe, Bob digs himself in deeper and deeper as he Cannot Spit It Out until she's managed to get a chance to perform in front of an audience as an Idol Singer. It's only then, at the last minute that the truth comes out. Due to the Snap Back clause in sitcoms, Bob is Easily Forgiven because he's a true friend for telling her in the end, even though he'd been lying to her for the whole episode.

Contrast to A Simple Plan or Zany Scheme as the plot is pretty much the main character doing nothing, while their friend obviously make a fool of themselves. A Snowball Lie may be involved. If this persists over a period of time, Alice may be Giftedly Bad.

Not to be confused with Digging Yourself Deeper, for awkward conversations, or Dug Too Deep, for actual digging.

Examples of Dug in Deeper include:

Singing

Film

A variant occurs in Citizen Kane, only without hilarity ensuing.
- Subverted by the fact that Susan knows that, while she's not completely untalented, she's nowhere near good enough to carry an opera all on her own. It's only Kane using all his wealth and influence to push her into the spotlight against her wishes.

Live-Action TV

Hannah Montana: Lilly thinks she can sing, Miley meanders around telling her the truth, but then Lilly steps up for Karaoke Night, you know the rest...
Leonard goes through this with Penny in one episode of The Big Bang Theory. And then the ensuing Snowball Lie just keeps getting worse under Sheldon's influence as well...
Cake has this with Cake, Amy and Benjamin trying not to hurt Miracle. Slight variant in that she finds out before doing anything stupid, when Benjamin is unable to edit a tape of her singing.
An episode of That's So Raven puts an interesting spin on this trope. Corey's band holds auditions for a singer, and a Hollywood Tone Deaf girl shows up. Corey falls in Love At First Sight and as a result is unable to hear how bad she sounds so he chooses her. His other bandmates had to record her singing and play it back for him to get him to realize what she really sounded like.
Kamen Rider W has a variant with a plot based around a Dopant that causes people to unquestioningly believe specific lies that makes the judges on a Talent Show believe the lie "Jimmy's music is good". Jimmy's success on the show, combined with praise from his girlfriend (who was lying to him to make him like her), makes him delusional about what people think of his music when everyone actually hates it with a violent passion.
One episode of Two and A Half Men has basically the exact same plot as the example in the description. Charlie pretends that an old flame can sing because he's kinda hoping to sleep with her but keeps kidding himself that he's just being friendly.

Western Animation

Hi Hi Puffy AmiYumi: In the episode "Song Sung Bad", Kaz decides he has what it takes to be a singer. So straight that it actually hurts.
Doug has this trouble with Patti during a singing contest.

Some non-singing examples

Anime and Manga

In Ranma ½, Ukyou finally unseals the Special Sauce she made ten years ago and has been aging since... and is promptly knocked unconscious by it. She doesn't know (but Ranma does, and remembers) that Ranma accidentally spilled it just after she first made it, and replaced it with a foul concoction of everything he could find at the time. Instead of telling the truth, he keeps eating whatever she slathers the "sauce" with, refuses to acknowledge it's bad, and claims to Akane that there's nothing wrong. Then Ukyou thinks that he's saying this because, back then, he promised to take care of her for the rest of her life if it tasted good, so this must mean he loves her!

Live-Action TV

The Jeffersons: Everyone except Florence told Louise they like her paintings even though they were awful. She got a show, and then George finally confessed that they were just encouraging her. She didn't believe it and sold a painting for $500, proving them wrong - until the purchaser revealed he only wanted it for the frame and threw the painting in the trash.
Exactly the same thing happened to Lily in How I Met Your Mother. Except in her case a Veterinarian then found the painting in the trash and hung it up in one of his exam rooms, later discovering that the painting somehow has a calming effect on dogs, which leads Lily to start marketing her paintings to Veterinarians. Tragically, Lily's paintings cause birds to kill themselves.
The Andy Griffith Show: The good folks of Mayberry try to get town drunk Otis to stop drinking by giving him a hobby: painting. Everyone praises Otis' work despite its lack of quality for fear that he'll be back to the bottle. The painting makes it all the way to the auction block before Otis realizes everyone hates it. Not discouraged, he paints a second picture, and it's a masterpiece, because he did it while drunk.
- A similar plot happened when Aunt Bee made pickles that qualified for the county fair.

Radio

Adventures in Odyssey: Julie tells Dwayne that she thinks he's funny. He begins playing the role of a comedian, telling a string of really corny jokes. Julie does nothing to stop him and soon Dwayne signs up for the school talent show. In the end Dwayne does a magic act, because his Dad told him offscreen how bad his jokes were.

Western Animation

Arthur and DW pretend to like Grandma Thora's food, which encourages her to contribute to the local bake sale.
Chowder's first episode involved the titular character being asked to cook food on his own. Unfortunately, he's distracted at a critical moment and adds poison instead of the proper ingredient. His mentor, Mung Daal, can't bring himself to tell Chowder he made a mistake, so he has to try and buy-or steal-all of the food from the stand Chowder sets up.

Mung: Why did I put the poison in the spice cupboard?