If your sim interacts with him enough, he will become "alive" for several hours during the day. During that time your sim(s) can interact with him like any other sim (all interactions, including romantic ones). Also before that happens he will also unlock his costume so you can dress your other sims up like him as well.
https://scontent-dfw5-2.xx.fbcdn.net/v/t1.0-9/35927130_1028466913970270_7402340877269467136_o.jpg?_nc_cat=0&oh=6a6b898f6c246629573d442c892703ea&oe=5BA28B55
https://scontent-dfw5-2.xx.fbcdn.net/v/t1.0-9/35973330_1028466870636941_5385812981147762688_o.jpg?_nc_cat=0&oh=993c3975676c4aa693225d9e656d0a37&oe=5BA8D08B
https://scontent-dfw5-2.xx.fbcdn.net/v/t1.0-9/35935198_1028471757303119_2750010771571212288_o.jpg?_nc_cat=0&oh=1eb8037a85930db8c7bf2a7fdc30ea41&oe=5BE0327D
There is a small animation, but it happens very quickly. I happened to catch him "going" back to his tree.