True, Jimmy Olsen had some giant transformations, but he had some big ones too.
Back in the days before fat shaming, Jimmy added a few pant sizes....and a lot more!
Here's how those changes went....
The Fat Boy Of Metropolis
Here, Jimmy is visiting Professor Potter's lab to check on his newest formula, but the professor isn't there though his new assistant, Dr. Rance is.
The professor has a formula that increases size and weight in animals, and Dr. Rance gives Jimmy some, claiming to mistake it for a soda pop (as it is a hot day, though, Rance's "gift" seemed to be a set up).
Jimmy, continuing his cub reporter business, went to stay with editor Perry White who was helping him with a story, and due to the heat, slept on Perry's back porch. Jimmy awoke the next morning to be more than twice the man he use to be....so much so, he needed to borrow a Santa suit from Perry just to have clothes to wear. Jimmy still wanted to do his regular assignments, so he did (after being seen by a chimney by his girlfriend, Lucy Lane).
Getting a new suit, Jimmy tried skydiving, firefighting and a carnival interview (thankfully saved from danger by Superman, except in the last case, where Jimmy offended Lucy with a misunderstanding with the carnival fat lady). Still undeterred, Jimmy went to a planned interview with a maharajah on his boat offshore, where his extra weight would do him good....as the maharajah was to reward Jimmy with his weight in jewels for saving his life. Superman then took Jimmy and the jewels home to Metropolis, but, it was revealed that the maharajah was really Rance in disguise, who set this up to get Superman to take his stolen gems past customs. When Rance and his crew went to steal their jewels back, Superman was waiting. Professor Potter found a cure, and Jimmy, at his normal weight, got jewels from the real maharajah (and likely made up with Lucy as well).
Jimmy Olsen, Freak
Next up for a huge adventure for Jimmy is Superman's Pal, Jimmy Olsen #59 (March, 1962) by Leo Dorfman, Curt Swan and George Klein, with a cover by Swan and Klein.
This time, Jimmy is upset by the number of suitors Lucy Lane has on Valentine's Day (all of whom have better gifts than Jimmy).
Jimmy plots a way to make more money to buy Lucy some diamonds, when out of the sky comes a beautiful alien girl! It is Princess Ilona of the Sunev galaxy, who states she has been watching Jimmy's adventures for years, has fallen in love with him and wants to marry him. Ilona gives Jimmy a diamond studded belt, which gives him super powers like gravity control, the golden touch and invisibility. Jimmy now wants to take Ilona to Lucy's costume ball that night, to show her his new fiancee.
Jimmy goes as a "spaceman" and dances all night with Ilona in front of Lucy, then let's her know they are to be wed. Lucy is heartbroken as Jimmy leaves to get his belongings together to leave with Ilona the next morning. That morning, Jimmy, still wearing his spacesuit, meets four other aliens, who are Ilona's four husbands! The group take an instant dislike to Jimmy, using their power belts to make him fat, then grow his tongue, ears and hair as Jimmy calls for Superman with his signal watch. Superman shows up and knows the husbands, convincing them to change Jimmy back to normal, but tells Jimmy he can't pull out of the marriage without causing a galaxy wide war. Still, they come up with a plan, with Superman bringing two old hags Jimmy claims are his other wives who will have to come with them. Ilona disavows her plans, and leaves with her four husbands. The hags were really Lois Lane and Lana Lang in disguise, who Jimmy swears to secrecy about what they did, so Jimmy can make Lucy (Lois' sister) still sweat over not being nicer to him.
All in all, Jimmy was lucky that Lucy Lane still loved him for all he put her through, and that his weight problem was so easy to fix.