Knockscream

Knock Out x Starscream is the slash ship between Knock Out and Starscream from the Transformers: Prime fandom.

Canon
Knock Out was originally called to Earth by Starscream after Megatron was severely injured. They initially had a terse relationship, Starscream disapproving of Knock Out's affinity with street racing.

However, Starscream eventually decided he wanted to kill an injured Megatron and lead the Decepticons. He offered Knock Out the position of second-in-command, which he accepted. Though they were unable to complete the coup, it was the first time the two Decepticons got along.

After Megatron recovered, Starscream was injured and tended to by Knock Out, the ship's medic. When Starscream got more injured trying to retrieve a new arm, Knock Out showed concern and asked him to take care of himself.

The two's quippy relationship continued until the arrival of Shockwave, which got Knock Out demoted. He agreed to help Starscream with Dark Energon experiments, despite disagreeing with his intent. They accidentally set a Terracon loose on the Nemesis and were forced to hide. It was during this scene that Starscream admitted Knock Out was a friend and the medic complimented him on his finish.

Knock Out was assigned to work under Shockwave after the Terracon incident, lessening his interactions with Starscream. Their relationship worsened as a result, which came to a head during Predacons Rising. Starscream attempted to take over the Nemesis (which had been acquired by the Autobots) and insulted Knock Out when he made a quip. This caused him to knock out Starscream (no pun intended) and officially join the Autobots.

Fanon
While not the most popular ship in the Transformers: Prime fandom, Knock Out x Starscream has gained a steady following. This following increased during Seasons 2 and 3, the latter of which featured the Terracon incident.

It was confirmed by the producers that Knock Out is gay. Starscream's sexuality has not been mentioned, which had lead people to wonder if Knock Out was actually flirting with him and if he returned it.

On AO3, Knock Out x Starscream is the second most written ship for Knock Out and the ninth most written ship for Starscream. It is the sixth most written ship in the Transformers: Prime tag.

Fandom
Knock Out/Starscream tag on AO3.