I remember going to Sea World with my family for Thanksgiving my freshman year at BYU. The animal that made the biggest impact on me was the walrus. He was the fattest thing I'd ever seen. He couldn't even move. My sister leaned over to me and commented on how looking at a walrus is enough motivation to do whatever it takes to avoid the "freshman 15" [in my case, 30]. I agree. Look at this kid:

So, shortly following our little jaunt down to Florida, I got my tail in gear and started running again. I bought a gym membership and went every day. I've since fallen off that wagon. I'll start P90X and stop a week in. It's just not my thing.
I need some motivation. I could run the half-marathon on the same day as his marathon in June. I haven't committed yet. What do you think? And if you've got a surefire way to motivate yourself to get moving, I'd love to hear it!