OK, color me convinced. It's all in the belt.
Here's a picture of Paul McCartney presumably not in Springfield:
And here's the one published in the SJ-R:
Look at his belt. Same one. I'm not sure even a dedicated imposter could get that detail right.
I'm also not sure I like the belt though.
HT to Dave Bakke at the SJ-R for the top pic (and the SJ-R article for that matter).