While the Avengers are unlikely to make an appearance in the upcoming Invincible series from Amazon, the title hero has bumped into them in the past. Mark Grayson may not be a household name just yet, but he still managed to tag along on an adventure with everyone's favorite web-slinger, Spider-Man.
Created by Robert Kirkman and Cory Walker, Mark Grayson was the son of Omni-Man, the greatest superhero on the planet. Mark inherited his fathers abilities of super-strength, flight and durability when he became a teenager. After swearing to protect the world, he discovered that his father was part of an alien race called the Viltrumite, whose sole purpose was to conquer and enslave the universe. After a huge confrontation, Omni-Man left Earth, leaving Mark as one of the most powerful beings on the planet.
Later in the series, a man named Angstrom Levy captures Invincible's mother and brother, and sends Mark through multiple dimensions in an effort to weaken him before a final battle. One of the dimensions, as discovered in 2006's Marvel Team-Up #14 by Robert Kirkman, Cory Walker and Bill Crabtree, is the Marvel Universe.
Mark emerges from a portal next to where Spider-Man is currently fighting Doctor Octopus, accidentally slamming the villain through a wall. After mistakenly believing Octopus has super-powers, Invincible flings him across town, causing Spider-Man to scold him quite harshly, telling him that he could've killed the villain.
After Invincible explains his situation to the web-slinger, Spider-Man says he can stick by him and help find Doctor Octopus, who went missing after being thrown across New York. He takes the young hero to Avengers Tower, reasoning that the hero team would have the means to locate him within the city. When they arrive they are greeted by Aunt May and Mary-Jane, and then Spider-Man reintroduces himself to Mark as Peter Parker. The Avengers arrive, and Invincible tries to name them in the same way that Peter has named his superhero alter-ego, e.g. Captain America as "Flag-Man" and Wolverine as "Claw-Man." After Iron Man gives them a lead, the two heroes leave to stop Octopus.
It turns out, Doctor Octopus was waiting for them, causing as much destruction as possible in order to attract their attention and kill them. After a brief scuffle, Invincible becomes frustrated and rips the robotic arms off of the villain, ending the fight. As if on cue, another portal opens, signaling that Invincible has to go to save his family. Spider-Man attempts to hitch a ride, wanting to help the young hero, but his web is cut off before he can follow him.
While often seen as a relative youngster in the Marvel Universe, this one-off issue got to show us Peter in a more father-like mentor role. The two heroes do still share some qualities, most noticeably using quips and levity in almost every situation, but this slightly more grown-up Spider-Man appears to be more like a goal for Invincible to strive towards in terms of reaching his potential as a hero. Peter has restraint that Mark fails to show in his confrontations with Octopus, explaining that he can't just lash out in anger, something Spider-Man is all too familiar with. Mark also shows wonderment when introduced to Peter's wife, stating "You hit the jackpot", which links to the many relationship issues he himself has had in his own series.
Ultimately, outside of this crossover, the two are very different characters. While Spider-Man often dips into darkness, he tries his best to be light and fun, and attempts to do things relatively inside of the law, as much as a vigilante can. Invincible, however, lives in a much darker universe, and often has to rise, or lower, himself to meet that darkness, not being adverse to a little brutality every now and again. While it was nice to see these two heroes cross over, especially with Peter in adulthood and Invincible still developing himself as a hero, it's unlikely that the two heroes would now see eye to eye with each other.