Chitauri are a race of aliens the serve Thanos.
Impossible Man was working on a documentary on the Chitauri until they spotted him and chased him across the galaxy. Impossible Man made a television series starring Falcon so that he can be ready to fight off the Chitauri. When a Chitauri scouting party arrived on Earth, Falcon and the rest of the Avengers ended up fighting the Chitauri to keep them from getting to Impossible Man. Falcon then convinces Impossible Man to send the Chitauri far far away from Earth by deputizing him in one scene as an Avenger. Impossible Man shapeshifts into an intergalactic missile to send the Chitauri far far away from Earth.