A little Foreshadowing there - while all of the heroes are deadly serious, these two are having fun. (This would become a plot point in Issue #4.)
That particular scene was similar to the appearence scene of the Squadron Supreme at the begining of Kurt Busiek's run on the Avengers. "Five gets you ten they're mind-controlled!" is to point that Hawkeye is Genre Savvy and realizes the Recycled Script (the Squadron Supreme was indeed mind controlled back then). Of course, only the scene was similar, everything else that followed was different. As he pointed when he complained that the boomerang arrow would have worked with Whizzer; it did work with him.
"HEL-LO!WERE YOU EVEN LISTENING TO YOURSELF?! 'Stick to the plan,' he says. 'Observe and move on,' he says. But does he follow the plan? Or does he spend twenty minutes beating up some LOON in Kevlar to save some drug dealers?!" (Shown above.)
In the background of one splash page we see Batman doing a flying kick straight through Vision. The look on his face is priceless◊.
From the same page: The expresssion on Plastic Man's face while Quicksilver ties his body into knots.
Both funny and awesome; in issue 4, Wonder Woman decides to fall back while the assembled heroes moved forward, to take on any threats from behind. Just as she prepares to battle Surtur, She-Hulk and Hippolyta offer to help her.
She-Hulk: Hey, Star-shorts! Figured you'd be bored here by yourself so I thought I'd hang with you. We can talk girl-talk. Y'know, kicking butt, taking names, like that.
It also counts as a Crowning Moment of Heartwarming, as Hippolyta (from her Wonder Woman stage) also asks to join her. Keep in mind, she was dead at the time.
Firestorm looks a bit disturbed with Uatu looking right into the Watchtower.
Firestorm: I need to go to the bathroom. But what if he sees through the walls...
Vision and Aquaman meet in a snowy Metropolis as time and space collapse around them. Neither of them quite knows what is going on, and Aquaman attacks the Vision in frustration. Vision's response:
Vision: But perhaps, since we do not know our circumstances, we should refrain from killing one another until we know more. Aquaman: ...point taken.
Ben Grimm's brief visit to the Batcave. "Yer idea a' small change, huh?" (Referring to the giant "Bad Penny" trophy.)
Manhunter's inability to read the minds of the Marvel Universe's denizens in one issue is a constant Running Gag. Even he admitted it was getting on his nerves.
Quicksilver's growing envy that his speedster counterpart The Flash has his own museum.
Hawkeye and Green Arrow's rivalry through out the story is hilarious to watch.