Sigmund Caesar initially moved to Ponyville in order to visit his little brother Slowhoof, but immediately made friends with several ponies around town and decided to stay and set up a psychology clinic. Along with his brother, Sigmund grew up in Canterlot, being the elder child of the family (he considers himself to be much older, despite the fact that he was only born a year or two earlier). He was always considered the more intelligent of the two, but was extremely skiddish, and could only be made to leave the house by force (he was part of a scout troop along with Blues, and complained on every camping trip). Eventually, he went on to graduate from one of the finest universities in Canterlot, earning a degree in psychology. Sigmund currently works and lives at his own personal office, the "Caesar Psychology Clinic".
Sigmund has a shoulder-length, wavy mane, and is slightly taller than the average stallion, but not as tall as his brother. He isn't exactly the toughest pony around, but he's far from un-fit, fully capable of defending himself, and he has a blue belt in Taekwondo to prove it. His vision is slightly impaired, so he wears a pair of dark grey, thick-rimmed glasses.
Sigmund's mark is a blue "frowny-face", which he earned by assisting friends and family when they were sad. This talent for consolation and reasonable advice is what gave him the idea for becoming a psychologist. He finds the fact that the face frowns ironic, since he makes ponies smile, but he has decided to think of it as a "welcome sign" for those with struggles.
Sigmund is a generous, amiable stallion, who tries his best to treat everypony he meets very well, but he tends to show favoritism at times. He is very skiddish, which can endanger both himself and others at times.
Being a unicorn, Sigmund is capable of performing spells, but he only knows a few (his signature one being his "calming spell", along with minor healing spells, and levitation). As previously mentioned, he is also a blue belt in Taekwondo, though he dislikes resorting to violence. Sigmund is currently teaching himself to play the violin, and (although it isn't exactly a "skill") has the ability to walk on/ride (he uses a levitation spell to move them) clouds, due to a potion Hay Wire gave him.
Sugar Frost - Sigmund met Sugar one night when he wandered into Sugar Cube Corner during a party. Her vivacious and lively demeanor immediately caught his attention, and he soon developed strongs feelings for her. He is always willing to do whatever he can to make Sugar happy.
Shan Xing - Shan was the first pony Sigmund met in town, and the two quickly became friends. Sigmund respects Shan's overall character (physical prowess with gentle nature, mainly) and loves his special tea.
Slowhoof Blues - Being Sigmund's younger brother, the two have obviously known each other very well for a very long time. Although they don't interact frequently, they enjoy each other's company. Sigmund admires Blues' talent for music.
Sigmund as made several other close, respectable friends in his short time in Ponyville, and he hopes to make many more.