Coulson because the last time he sent the rest of the team out they came back with twelve boxes of cereal that all contained special surprises inside, and they immediately sat down at the table and started comparing Star Wars trading cards (only inside specially marked boxes of Lucky Charms).
kills the spiders
They live on a plane, so the presence of a spider is usually a big deal. Like, “Simmons come here it’s a rare species of Brazilian spider that’s been living on the plane since we landed there two months ago come look!” big.
comes home drunk at 3am
Occasionally when they land for longer than a day, Skye will drag everyone out to “see the sights” (read: get drunk in whatever city they’re in), and at the end of the day it’s her and Fitzsimmons that end up the most hammered. May is superhuman, Ward doesn’t drink enough to get too drunk, and Coulson has taken it upon himself to be the babysitter.
For the first month of their unexpected journey, everyone is super professional and independent. Then one day they wake up to see Coulson wearing a Captain America apron and making pancakes, and that basically settles that. He makes fucking awesome pancakes.
remembers to feed the fish
Nick Fury vetoed the fish tank. Boo Nick Fury.
decorates the apartment
If by apartment you mean bus, the answer’s mostly SHIELD. But each of them starts to make parts of the plane their own. No one comments on this until they realize that every. single. cabinet. on the entire airplane has been labeled (“bowls,” “scissors,” “May’s drawer do not open.”), and everyone looks over at Fitz who sheepishly puts the label maker down on the table.
Skye sings basically 24/7, and it’s usually Coulson who joins in first. One day she starts singing Fergalicious and he belts it out along with her, and everyone gets quiet except him and just looks at him and wonders how they ever missed this vitally important part of their team leader.
falls asleep first
Coulson “goes to get some work done” at like 11, but everyone knows he’s going to bed. Their suspicion is confirmed one night when they have to make an emergency landing and he awkwardly shuffles out wearing a SHIELD t-shirt and Captain America pajama pants.