I got a ukulele! This isn't perfect though, since the person who wrote these tabs (not me) made a few mistakes. I fixed the one toward the end, but there's one in the beginning that I'm not sure how to fix. Here's the tabs anyway, if you'd like to take a look at them (I didn't do the uke #2 background strumming because A, its confusing, and B, I'm lazy) : https://tabs.ultimate-guitar.com/b/brad_breeck/gravity_falls_theme_ukulele_crd_1753885id_22072015date.htm
Background poster thing was created by somebody on Tumblr, I'm not sure who, but here's where I found it XD http://gravi-teamfalls.tumblr.com/post/124077183233/sachinteng-gravity-falls-comic-con-poster-for I am also not responsible for any inappropriate content you view on tumblr, so do not report me if you see something bad on there. It's not MY fault, and I must give credit to the original creator.
