I received a Classic Game Room shirt in the mail today. It also came with an autograph from Mark!
Very cool!
You better slab that in a CGC case! I know it sounds silly, since Mark isn't a big celebrity, but that's exactly why that will probably be worth money in a decade or so.
When the 2000s nostalgia wave hits, it will be those harder to find autographs that become worth money. People like Stan Lee and Scwartzenneger may be bigger stars, but they sign autographs so often that they're not rare or valuable at all.