Marvel (then called Timely Comics) first showed that they had a shared universe with policewoman Betty Dean talking about the Human Torch (Jim Hammond) being an member of the police force to the Sub-Mariner, to which the villainous Sub-Mariner replied "I've heard of him. So you think that little flame can hurt me? Hah!", in Marvel Mystery Comics #7 (May, 1940) "Rampage In New York" by Bill Everett.
The Human Torch (Jim Hammond) met for the first time and fought the Sub-Mariner, who was essentially a super-villain before becoming a superhero, in Marvel Mystery Comics #8 (June, 1940) "The Human Torch and the Sub-Mariner Meet" by Bill Everett.
Captain America, Bucky, the Human Torch (Jim Hammond), Toro, the Sub-Mariner, the Angel and the Black Marvel first appeared together in All-Winners Comics #1 (Summer, 1941) "All Winners" by Stan Lee and Ed Winiarski.
Bucky, Toro, Tubby, Knuckles, Jeff Worthington Sandervilt and Whitewash Jones first appeared together and formed the Young Allies in Young Allies Comics #1 (Summer, 1941) "The Coming of Agent Zero" by Otto Binder and Charles Nicholas.
Captain America, Bucky, the Human Torch (Jim Hammond), Toro, Sub-Mariner, the Whizzer and Miss America form the All-Winners Squad in All-Winners Comics #19 (Fall, 1946) "The Crime of the Ages" by Bill Finger and Syd Shores.
The Fantastic Four first met the Sub-Mariner, who was back to being essentially a super-villain, in Fantastic Four #4 (May, 1962) "The Coming of Sub-Mariner!" by Jack Kirby and Stan Lee.
Spider-Man met the Fantastic Four in The Amazing Spider-Man #1 (March, 1963) "Spider-Man vs. The Chameleon" by Steve Ditko and Stan Lee.
The Fantastic Four first met and fight the Hulk in Fantastic Four #12 (March, 1963) "The Incredible Hulk" by Jack Kirby and Stan Lee.
The Hulk, Thor, Iron Man, Ant-Man and Wasp first appeared together and formed the Avengers in The Avengers #1 (September, 1963) "The Coming of the Avengers!" by Jack Kirby and Stan Lee.
Spider-Man, Captain America, Thor, Tony Stark (Iron Man) in [FONT=Verdana, Arial, Helvetica, sans-serif]
[FONT=Verdana, Arial, Helvetica, sans-serif]a top hat[/FONT][/FONT], [FONT=Verdana, Arial, Helvetica, sans-serif]
[FONT=Verdana, Arial, Helvetica, sans-serif]Daredevil, [/FONT][/FONT]Nick Fury, [FONT=Verdana, Arial, Helvetica, sans-serif]
[FONT=Verdana, Arial, Helvetica, sans-serif]Dr. Strange, [/FONT][/FONT][FONT=Verdana, Arial, Helvetica, sans-serif]
[FONT=Verdana, Arial, Helvetica, sans-serif]Quicksilver and Hawkeye [/FONT][/FONT]attended Mr. Fantastic's wedding to the Invisible Girl in Fantastic Four Annual #3 (1965) "Bedlam at the Baxter Building!" by Jack Kirby and Stan Lee.