Their treehouse is heavily decorated. The "T-E-R-R-I-F-I-E-D" carving isn't the only one, I like to think the whole floor and walls are carved with random stuff. Honestly, that one time when Josh asked Tyler to carve how he felt definitely isn't the first time they did that.
Tyler writes and draws a lot. Sometimes almost realistic, sometimes a bunch of abstract shapes, depending on his mood . A bunch of these are laying around the treehouse, the most important ones taped to the walls.
Josh keeps a bunch of stuff he likes on the treehouse, especially things he wouldn't trust around his parents, too scared they would take them/destroy them.
They both brought a bunch of pillows and blankets and made a cozy nest in a corner, where they're always snuggled up together, sometimes even spending the night, especially in summer.
They don't have electricity in the middle of the forest, but they still have battery powered fairy lights. They probably both have MP3 players but when they listen to music, they use the same one, sharing the earphones. One of them would have one of these portable DVD players and they would watch the same movies over and over until the battery would run out.
They have a tire swing! And they really like it.
They live in different towns, the forest separating the two. The treehouse is somewhere in the middle.
Tyler doesn't go to school anymore, he dropped out in early middle school. Josh still goes to school, but he often skips to stay with Tyler instead. When he does go to school, Tyler waits for him at the treehouse.
They love summer. Because they can spend more time together, and at the treehouse. When the weather is nice, they can sleep at the treehouse, and stay late outside looking at the stars and picking flowers.
When it's colder, like in winter, they still go outside to play around, but they spend more time indoors in Tyler's room. They don't go to Josh's because his parents suck.
Josh's hair is always colorful, before being blue it was red. He dyed it blue to surprise Tyler, because it's his favourite color. It's his favourite because his synesthesia sees Josh as blue. Before that, he used to hate blue.