Marvel Animated Universe

Marvel Animated Universe refers to a fictional universe which connects a number of animated TV shows based on Marvel Comics. The original universe was seen in the 90's, but it was rebooted and remade into the modern animated universe.

Shows
X-Men: Animated - The show which began the animated universe. It lasted for five seasons and was based on the 1992 X-Men animated series.

Spider-Man: Animated - This show created continuity with X-Men by having characters from X-Men appear. It lasted for five seasons and was based on the 1994 Spider-Man animated series.

Iron Man: Animated - The first season of the show showed no signs of continuity, but Iron Man later appeared on Spider-Man and the second season of the show featured Hulk, creating a continuity with the Fantastic Four and the Incredible Hulk. It lasted for two seasons and was based on the 1994 Iron Man animated series.

Fantastic Four: Animated - These characters also appeared on Spider-Man and the Hulk was featured on the show, further establishing continuity. It lasted for two seasons and was based on the 1994 Fantastic Four animated series.

Hulk: Animated - This show featured the same version of the character which had appeared on Fantastic Four and Iron Man. It lasted for two seasons and was based on the 1996 Hulk animated series.

Silver Surfer: Animated - This is a prequel to the Fantastic Four as it tells the origin story of the Silver Surfer, who had appeared on the show. It lasted one season was based on the 1999 Silver Surfer animated series.

Avengers: Animated - This takes place in the future and featured Iron Man and Captain America. It lasted one season and was based on the 1999 series Avengers: United They Stand.

Chronology
Silver Surfer: Animated - This is believed to be the earliest point in the continuity. It tells the origin story of the Silver Surfer and sets up his relationship with Galactus.

X-Men: Animated - This is believed to be the earlist point in the continuity which set in modern day. The X-Men have already been established at the start of both Spider-Man and Iron Man.

Spider-Man: Animated - It is believed that Peter Parker is granted his powers at some point during the first season of X-Men, as he remarks that the world may fear him because of his mutant powers. The episode featuring the Fantastic Four occurs prior to the finale of the Fanastic Four series.

Iron Man: Animated - Tony Stark is also believed to become Iron Man at around the beginning of the second season of Spider-Man. The Hulk episode takes place prior to the second season of the Hulk show.

Fantastic Four: Animated - This show takes place shortly after Bruce Banner becomes the Hulk.

Hulk: Animated - This show takes place shortly after the character's appearance on the Fantastic Four.

Avengers: Animated - This show takes place years after the end of most previous shows. Iron Man and Captain America both appear but are much older, setting this show at some point in the future. It takes place at the very end of the timeline.