According to Roadside America website, they're big. they're scary and there are hundreds of them. The site has a page on the "origin of the species" that you can read more here.
Apparently, in 1999, Steve Dashew stumbled onto the site, he was the owner of International Fiberglass, the company that turned out thousands of commercial statues in the 1960s and 70s. International Fiberglass took a single statue mold created for a cafe and parlayed it into a roadside industry. Roadside America interviewed Steve which you can read here.
The first figure was a Paul Bunyan, done for the PB Cafe on Route 66 in Flagstaff, Arizona in about 1962. Most of the statues were derivatives of that one mold. You can find more info on this site
There was Miss Uniroyal, in bikini and dressed version.
The Alfred E. Neumans, "Happy Half-wits", which apparently one is/was in Seaside Heights and held the Paul Bunyan axe, I have to take a ride there to see if he's still standing, and the one I saw in Jackson.
They were also made for various other establishments. Here's two common ones, the "Indian Brave" in Bemidji, MN and "Salsa Muffler Man", Malibu, CA.
During my research I ran into Roadside Architecture website which has lots of information on Paul Bunyan Muffler Man and on giants of the road including the huge gorilla at Mighty Joe's Gas Grill & Deli in Shamong, NJ which I have run into a few times. I don't have a picture of my bike in front of him.
Visit Roadside Architecture website here if you interested in getting pictures of your bike in front of a giant, they are found all over across the country.
List of sites mentioned:
Wikipedia - Alfred E. Neuman link
Wikipedia - Muffler Man link
Wikipedia - Paul Bunyan link
Roadside America - Origins of the species link
Roadside Architecture - list of giants of the road link
Ratrun - You will find a pretty big list of Muffler Man on this link