Temmie or her followers can only be found if the game has a certain FUN value. From the information her followers give to the player, it is known that Temmie founded colleg, the most famous college of the realm.
She was also the royal scientist before Sans. One of her most famous scientific experiments is the creation of Temmie Flakes, a powerful magical food. Temmie eventually mysteriously disppeared as a result of eating too many Temmie Flakes at once.
Temmie is known to speak in broken English, similarly to her counterpart in Undertale. Her followers also talk in this way even though in Undertale, Gaster's followers speak normally.
While it is unknown how exactly Undyne and Temmie are connected, it is known that there is a connection between the two. Undyne has a Temmie related ability in her battle in the genocide route and her secret room contains a college graduation cap, possibly hinting that Undyne graduated colleg at one point.
Temmie is known to have 3 followers who only appear when the game has certain FUN values. They seem to greatly respect Temmie.
While it is unknown how exactly hooman, one of the FUN value characters, is connected to Temmie, it is likely that they are in a way, considering their name.