Strong Sad is the youngest of the Brothers Strong. He stands somewhere between Strong Bad and Strong Mad in height, and has large, elephant-like feet he calls "soolnds" (which, in the past, poachers have apparently offered thousands of dollars to obtain). His body is round and two shades of grey — a lighter grey from the waist up, a darker grey from the waist down. For some reason, however, Coach Z thinks he is yellow. Strong Sad's body makes the sound of an inflated rubber ball when hit — and according to Strong Sad, it is hit often. In One Two, One Two, Strong Sad hits his belly rhythmically, as one of the selectable tracks. His head is white and has an odd lump on the top, referred to as a "disturbing soft-serve flip" by Strong Bad in keep cool (a trait shared by Mr. Bland). It is unclear whether or not he has teeth. Strong Bad claims that he does not, but Strong Sad was seen brushing his teeth in narrator and concert. He is usually very calm and soft-spoken, although he has become hyperactive on occasion (at least once under the influence of caffeine), and he has also temporarily (albeit involuntarily) become a boisterous radio DJ once or twice. The phrase "covered bridges" seems to be able to put him in some type of trance, as seen in "Fall Float Parade". He also has some sort of reaction to sunlight overexposure, causing him to become uncharacteristically happy, even if he did not enjoy it (at one point, he actually asks to be shot). Despite his pale skin, he has apparently never been sunburnt, though he became moonburnt on at least one occasion.
Once, Strong Sad's main defining characteristic was his chronic depression, which overshadowed his high levels of intelligence and creativity. He has even been quoted saying "Each day, we die a little more." several times. Lately, however he appears to have recovered and rarely expresses sadness. His many interests include listening, books, listening to books, calligraphy, safety, being alone, arts, crafts, and arts b/w crafts. He has outstanding penmanship, often writing poetry, which he then recites at his own "poetry slams". Strong Sad is seen using both his right and left hands to write and play the guitar, implying that he is ambidextrous. He has been seen practicing T'ai Chi. Strong Sad also enjoys playing board games, and he seems to enjoy going to science-fiction and fantasy conventions, as seen in different town and TrogdorCon '97. He has an iPod, and he occasionally updates his blog from time to time. Strong Sad's highly philosophical view on life has creeped out other characters more than once, most notably Strong Bad and Marzipan. Strong Sad may have a crush on Marzipan; he has occasionally lied to Marzipan just so he could spend time with her, as in Marzipan's Answering Machine Version 10.2. However, he might just be trying to make friends with anyone he can.
Strong Sad has a love-hate relationship with his brother Strong Bad. It appears that the two got along quite well when they were younger, but nowadays, Strong Sad suffers almost constant abuse from Strong Bad. In particular, Strong Bad has quite a list of names he has used to insult Strong Sad. Strong Sad has also been the subject of numerous practical jokes by Strong Bad, Strong Mad, and The Cheat, ranging from being drilled a new navel by Lil' Strong Bad to being used as a stunt double for the Dangeresque movies, to even having wildebeest pheromones washed into his laundry. In turn, Strong Sad holds a very low opinion of his brother and considers him to be a clueless weirdo. However, evidence from "The Secrets That I Keep" suggests that even though Strong Sad insults Strong Bad, he also looks up to him and misses the days when they got along. He seems to retain some degree of brotherly love toward Strong Bad: when the Tandy 400 exploded in the email gimmicks, Strong Sad sincerely asked Strong Bad if he were all right, and wrote a letter wishing him well while Strong Bad was incarcerated. However, he also stated that his brother's absence caused him to feel far happier with himself than usual, and that he turned Strong Bad's computer room into his tai chi space. He was also eager to help Strong Bad with his 150th email in Sbemail 150?!?, and even managed to provide the background music for Strong Bad's email intro in alternate universe.
Strong Sad's troubled relationship with Strong Bad seems to have affected his social interaction habits with the rest of the community of Free Country, USA. He is generally reclusive and has only a few friends — his best friend appears to be Homsar, and he plays Jenga with The Cheat on Tuesdays. Early in the site's history, Homestar Runner even counted Strong Sad as a friend, and still shows some signs of friendship towards him. He is often overlooked and ignored when he has an idea, and he is sometimes even believed to be dead. Despite all of this, he serves as a loyal officer in the Homestarmy, temps at an unnamed computer company with Strong Bad and Homestar, and even has a Strong Sad Lookalike Contest held in his honor/insult each year.
Strong Sad seems to be the most rational of the characters, and often seems to react perplexedly to the others' cartoonish antics. He can often be found patiently correcting another's apparent mistakes, such as in TrogdorCon '97 and technology, or being entirely uncomprehending of the nonsensical events around him. He was even featured as the sole "Bear Holding a Shark Skeptic" in myths & legends.
There may be more to him than meets the eye, however. Occasionally Strong Sad has done things that are not in line with his usually calm temperament: He threw snowballs (saved in the freezer since he was eight) at Strong Bad, being physically violent, and he had a long bout of maniacal laughter when it was revealed that he was behind the whole DNA Evidence event. Also, when he was coerced into being the security guard in Baddest of the Bands, he tasered Strong Bad whenever he annoyed him. He also states in his blog that his resolution for the new year is to not feel so bad about wanting to hit Homestar so much, which is another example of his violent self.