Steve sighs and looks up from his drawing. He's pretty sure even in the modern time a phone should not be able to announce that without using a ringtone or text to speech capability. However, it's a StarkPhone so anything is possible. He wouldn't be surprised if the phone also records his movements and reports it to Stark or SHIELD.
The problem with Tony calling for Avengers Assemble is that two out of three times the call isn't really related to saving the world but more about saving Tony, mostly from Pepper. The last assemble initiated by Tony was because it was their fourth year anniversary - that alone was a miracle that Tony could have a long term relationship with anything humanoid, let alone Pepper - and he didn't know what to get for Pepper as a present.
The look from the rest of the Avengers was interesting once they knew the purpose of Tony's call for assembly. Natasha mentioned something about neutering someone to save the gene pool. Clint said the way to a girl's heart is a pair of throwing knives, Steve suspected that it was a Freudian slip on Clint's part. Thor suggested a taser to protect Pepper from any assailant since she was the girlfriend of a mighty warrior. Bruce, the only one who had sort of a normal relationship with a woman when he was not on the run, suggested expensive dinner and jewellery. Steve agreed but said he'd rather give a more personalized gift to a woman to show his sincerity rather than jewellery but it was up to Tony.
Tony surprisingly took it all to heart. He said he'd combine all the suggestions and decided he'd personalize an Iron suit for Pepper which sort of works like his Iron Man suit but could also throw knives and taser people. He'd present it to Pepper during their romantic dinner.
Steve should've seen this coming. He didn't expect Tony to take their suggestions so seriously. He was sure only Thor and Clint agreed with this gift choice. Natasha said she'd really want to pay for a ticket to see the look on Pepper's face when he presented the gift. All of them actually really wanted to, even Steve. JARVIS said he'd take pictures if he could.
Back to the assembly business, there's a one out of three chance the call is genuine and he'd blame himself for the rest of his life if he doesn't go. That's the reason he drives his motorbike all the way from Brooklyn to the big ugly building called the Avenger Tower at midnight. He really regretted calling it ugly because it ended up as their headquarters. He guessed it's karmic retribution for him not being so nice to Stark.
JARVIS lets him in and he takes the lift to the top floor which is now serving as the Avenger's meeting room. He's the last one to arrive. Bruce is already there since he's practically joined at the hip with Tony after the Loki incident. Thor is there since he can fly. He's surprised that Natasha and Clint are already there.
"Oh finally, the Spangly soldier decides to grace us with his presence," Tony teases.
Steve's used to this and just says, "Well, I live across town and I try my best."
"Well, if the world is ending, a few minutes make a big difference," Tony says dramatically.
Steve slightly pales and continues. "What's the problem? Please brief us quickly!"
Tony pouts and says, "My friend, the world is coming to an end because apparently people write fanfictions about us!"