Sizzy

Sizzy is a het ship between Simon Lewis and Isabelle Lightwood from The Mortal Instruments.

The Mortal Instruments
The two met through Simon's best friends Clary Fray, after she discovers she's a shadowhunter and meet's the Lightwoods. The two don't spend much time together, but start dating before the events of City of Fallen Angels. Although he was also dating Maia at the same time, and the two break up. They do get together again, and this time stay together but with Jordan arrival, it's unclear if they would last, as simon and Izzy eventually end up together.

Fanon
On AO3, Sizzy is the third most written ship for Simon and the most written ship for Isabelle.

Fandom
AO3

Trivia
They are endgame
 * The ship name comes from the first letter of Simon's name, and Isabelle's nickname, Izzy.