As for the "serious" art:
I began painting in the spring of 2008, during my final quarter in grad school. Basically, my brain & soul were falling out due to stress/paper writing/general academic malaise and taking a community ed painting class seemed like a better option than crawling into the fetal position in my apartment. Painting has become my favorite outlet and a great means of personal expression. I love vibrant colors and conceptual art, which I hope shows in my work.
As for the "not-so-serious stuff that probably mostly appeals to 5-year-olds":
I've been doodling in my notebooks for a long time now. I probably would have had a higher GPA during undergrad had I not taken my notes in magic marker, but on the plus side I have some awesome t-rex drawings from that time period as a result. During college I started using MS paint, mostly because I think crappy drawings are funny. About 3 years later I invested in PS elements (because I was too cheap for anything better) and had a lot of fun adding more detail and shading to my free-time drawings. So much fun, in fact, that I finally took the Adobe plunge and started using Creative Suite and full-on Photoshop. There's a pretty striking difference betwixt my drawings from 2009 and those from late 2012 and onward...but I love all of them, from the super crappy ones of yore to the multiple-layered ones of today. There really is no reason for any of them; mostly, they're just things I think would be funny, which usually ends up involving a disproportionate amount of dinosaurs...and bears...and cats. But mostly dinosaurs.