Catchphrase: Lucy often says "Ewwwww!" when something goes wrong.
Can't Hold Her Liquor: The infamous "Vitameatavegamin Girl" bit where Lucy gets drunk from the alcohol in the medicine after repeated takes. In her defense, it was 23% alcohol by volume not proof, percent (46 proof).
Did Not Think This Through: More often then not, her plans tend to go off the rails due to not really thinking about the details all the way and running into unforeseen circumstances.
Fiery Redhead: Subverted. Lucy is 60% screwball, 40% spitfire and 0% redhead — she dyes her hair.
Guile Heroine: Lucy usually tries to use her wiles rather than her muscles to achieve her goals. How successful she is (and how long before it backfires) varies by the occasion.
Hollywood Tone-Deaf: Lucille Ball was no diva, but she was no slouch either, as seen when she starred in Mame. Lucy's ability to carry a tune seemed to run on Rule of Funny.
Jerk with a Heart of Gold: All her scheming, lying and selfish moments aside, at the end of the day Lucy was still portrayed a loving wife, mother and friend
Malaproper: Lucy misspoke words after getting drunk trying to film a commercial. That Vitameatavegamin is potent stuff.
Lucy: "Do you pop out of parties? Are you unpoopular?"
Red Baron: Often cited as "That Crazy Redhead" by most who meet her, especially celebrities.
Ms. Red Ink: While it never had any visible impact on the family finances, quite a number of plots involve Lucy outspending the limit on things like dresses, hats, and furniture.
Zany Scheme: Constantly, a lot of the humor of the show comes from Lucy coming up with a crazy scheme to a situation and it spiraling into disaster.
Ricky Ricardo (Desi Arnaz)
Bilingual Bonus: Since Desi was indeed Hispanic, Ricky would sometimes dip into speaking Spanish whenever he would get excited or mad.
Catchphrase: "Aye-yi-yi-yi-yi!" In one of the England shows, he translates it as 'Blimey!' to a confused Englishman. Hilariously, later on it turns out the phrase needs no translation for Italian.
Funny Foreigner: The series made a lot of jokes at Ricky's expense regarding things like his accent or other things related to his being from a different country. It was never malicious though and the show made sure to go out of its way to show that Ricky was a fast learner and accomplished entertainer and manager.
Malaproper: Ricky misspoke idioms at times, though this was due to English not being his first language.
The Straight Man: He's the normal guy who has to deal with his wife's (and sometimes his friends') crazy antics — not that he couldn't sometimes be pulled into a Zany Scheme.
Ethel Mertz (Vivian Vance)
Aww, Look! They Really Do Love Each Other: Ethel and Fred have a number of these moments, for all their bicker and back-and-forth nagging, but Ethel more so in general. Any slight indication that Fred may be spending time with another woman, Ethel starts sobbing at the prospect of losing her, "Beautiful, fat, old goat Fred".
Big Eater: Ethel enjoys her food. She was the butt of quite a few "fat" jokes from Fred. Rather hypocritical of him really, since, despite Ethel's enormous appetite, he was actually much more overweight.
Sarcastic Devotee: Ethel may be a faithful friend to Lucy, but she's not above making sarcastic comments.
Screw This, I'm Out of Here!: Usually whenever Lucy hatched up one of her schemes, she'd tried to bail first chance she got. She would never get far though.
True Companions: Despite all the headaches the crazed red-head would cost her, Lucy could always count on Ethel as a loyal and steadfast friend.
In "Equal Rights", he (and Ricky) rush down to a restaurant to protect Ethel and Lucy after the two trick their husbands into believing they're being attacked by armed robbers.
It reaches hilarious proportions in one episode, where Ricky is entertaining on a cruise ship; in earlier episodes with scenes set near large bodies of water, Fred mentions his seasickness (and once even got woozy on a ship that was tied off at the dock); however, Fred suddenly does a 180 degree turn, and actually turns into a romantic. Ethel is actually concerned about Fred's unusual behavior at first, but is eventually entranced at the idea of her and Fred having a second honeymoon, and basically spend the rest of the episode enjoying various different activities on the ship in a lovey-dovey manner.