Groot is a character in the Marvel Cinematic Universe (MFCU) who is also part of the Guardians of the Galaxy. Groot is an extraterrestrial being who belongs to the Flora colossus species, a race of arboreal humanoids capable of regenerating and controlling their own plant bodies. In the UCM films, Groot is portrayed as loyal and brave, yet innocent and sometimes childlike in nature. Groot has a very distinctive personality and his vocabulary is limited to the phrase "I am Groot", although other characters seem to be able to understand his meaning based on context and intonation. Groot possesses superhuman strength and stamina thanks to his wooden body, as well as the ability to regenerate and grow his limbs at will. He can also throw sharp spines and control the vegetation around him. Throughout the UCM films, Groot plays an important role in the fight against the forces of evil, even sacrificing himself to save his friends on one occasion. After his sacrifice, a new Groot is born from a branch, meaning the character is essentially immortal.
Captain America is one of Marvel's most iconic heroes. Created by Joe Simon and Jack Kirby in 1941, Captain America made his first appearance in Captain America Comics #1, just before the United States entered World War II. Since then, he has become a symbol of patriotism and justice in the Marvel Universe. Captain America is the alter ego of Steve Rogers, a frail young man who volunteered for a secret experiment that turned him into the ultimate super soldier. As a result, he has superhuman strength, endurance and agility, as well as exceptional leadership skills. With his indestructible shield, Captain America is a formidable fighter on the battlefield. Over the years, Captain America has battled many dangerous villains, including the evil Red Skull and the terrorist organisation Hydra. He has also led the Avengers on several occasions, becoming one of the most important members of the team.