This character is madly in love. How does the author of the story show it tot the audience? One possibility is to have them doodle their beloved's name and symbols of love.
It often includes Mrs./Mr. Crush's Lastname, both names in a heart, initials plus initials equals love, banal love rhymes, hearts struck by arrows or Umbrella of Togetherness. The person they are crushing on has no idea they're an object of their affection. It can also involve even more daydreaming, like doodling about one's Celeb Crush or Perverse Sexual Lust.
The person in love is likely to be doodling in a random piece of paper, in a diary or a journal. It's a way of expressing one's feelings privately, in a place nobody else is intended to see what they drew or wrote. Except for one's closest friends. If the journal with the drawings gets lost, the character gets embarrassed and ashamed. No one is supposed to see those silly, kind of embarrassing doodles, but to drive the plot further, it often happens that someone is going to see it.
Sweetie Graffiti is a sister trope. Unlike doodles, graffiti is public, and as such, it is almost always the result of two lovers wanting to express their love publicly and permanently. They document their childhood or teen love on walls, or they carve the symbols on a tree or pole.
Compare Secret Diary.
- While at the pens section of a stationary store to buy school supplies for Kanna in Miss Kobayashi's Dragon Maid, Tohru writes "I ♥ Kobayashi" several dozen times on a piece of scrap paper. Kobayashi is understandably creeped out.
- In Splendor in the Grass, Deanie spends one class period doodling in her notebook instead of paying attention. She writes her boyfriend's name over and over again, surrounded by hearts and in cursive as if in a wedding invitation.
- To All the Boys I've Loved Before: Love doodles (pictures of hearts, love letters, lovey-dovey smiley faces and boys' names written in cursive) are used for one poster of the movie. Appropriate for a movie about a girl who stores her secret letters to her crushes which she never sent.
- An early Animorphs story has Cassie and Rachel infiltrate their teacher's house to retrieve a doodle Cassie accidentally turned in with her test, featuring, according to Rachel, "a heart with the words 'Cassie loves Jake' and a really dorky cupid". Thankfully they're able to grab the offending item and leave before humiliation ensues (although Rachel insists that as Cassie's best friend, she won't say anything like "Awww, isn't that sweet?" or "Cassie is in lo-o-o-ve, Cassie is in lo-o-o-ve").
- Brooklyn Nine-Nine, "Boyle's Hunch": Detective Charles Boyle falls madly in love with a woman named Genevieve. At work, he doodles lovey-dovey stuff and shows the picture to his best friend Jake who assumes it's their wedding invitation. It's actually a picture of their joint tombstone.
- The Community episode "Physical Education" has the study group discover a doodle of Abed in one of their textbooks and go about tracking down the previous owner. They help Abed build up his confidence to ask her out. He does and gets accosted by her boyfriend who looks just like him, only Caucasian.
- Wizards of Waverly Place: Exaggerated with Alex's crush on Dean. Being an artist, her diary wasn't just filled with doodles- she drew herself a fairy-tale world in which Dean is a hero and she's a princess, which she uses magic to go into. Hilarity Ensues when, of course, this Secret Diary gets found by the Alpha Bitch.
- Dad: At the very beginning of "Dad Loves Mom", there's a brief shot of Dad writing in a notebook, which is filled with hearts and his wife's name written down repeatedly. It's enough to fill an entire page.
- Manic Pixie Dream Wife: At work, Chance realizes he's falling for his boss Serenity when he doodles her name and some heart shapes.
- The Nostalgia Chick: In episode "City of Angels", Nostalgia Chick is seen doodling love symbols in regards to her crush Todd in the Shadows.
- In Hey Arnold!, Helga is often seen drawing love doodles about Arnold whom she crushes on.