Are you talking about chinning like the black guys do on the playgrounds (pretend you're riding a bicycle while chinning, going side-to-side on the bar while bicycling, etc.), or just flailing about in space? If you are pretending to ride the bike, just to piss off TOD, well-played.
Regarding bulking up:
1. Since you are a delivery driver for a pizza shop, I'm sure they let you eat as much pizza as you want. If they don't, perhaps you should propose this new feature. I drove for a pizza joint my senior year of college, and was over 300lbs due to the frequent use of this policy as well as treating myself to fistfuls of mozzarella cheese whenever I'd visit the walk-in. Not the best method, but I guarantee you'll weigh more if you implement this regimen. I also won $40 off the other workers when I demonstrated the ability to eat 2 Big Macs in under 2 minutes, and $20 to drink 12 ounces of hot sauce without coughing or wincing at all.
2. Are you eating a full pound of beef at lunch every day? If not, start. I'd also recommend rotisserie chickens - they are ultra-cheap (only $5 at my local grocery store) and convenient. You only need a fork, as you can use the container they are sold in. Also at least a half dozen eggs each morning, with cheese, toast with jelly. It helps if you have a decent butcher who makes a decent sausage. Also, two full plates of dinner, every night. A protein shake made with egg-nog and whey is pretty tasty (and will help to put some pounds on).