The first offers a connection to Iron Man 3. In the trailer, there’s a scene in which Tony Stark and Peter Parker are walking and talking with Happy Hogan in the background. Peter is wearing a t-shirt with a little comic that says “I lost an electron,” and then the punchline, “Are you positive?”
This is the exact same shirt that Pepper Potts was wearing in Iron Man 3 when sleeping next to Tony Stark. Why he is wearing the same tshirt is a mystery, did Tony give it to him or… someone else… mystery mystery.
The next easter eggs is connected to the Civil War, and it looks like maybe there will be some scenes in Spider-Man: Homecoming that take place at the same time as the events in Civil War. There’s a point in the trailer where Tony is talking to Peter in the back of his car, the awkward scene where Peter thinks Tony is giving him a hug, when in reality he’s just reaching over to open the door for him.
If you look closely, Tony is rocking a bruised eye. This is the same bruise that Tony sustained during his fight with the Winter Solider. He’s trying to conceal the eye with a pair of sunglasses… at night. If this scene does take place during the same time as the events of Civil War or very shortly after, you have to hand it to Marvel for the attention to detail with their continuity.