I have an interesting Mesa story...
I was commuting from STL-ORF through CLT. The CLT-ORF leg i rode up front on a CRJ900 due to no open seats in the back. Both pilots had 4 stripes and I thought to myself that it must be OE or something... cool. It actually turns out that the captain in the right seat was junior manned to the right seat and was even senior to the captain in the left seat... that absolutely blew my mind! Junior manning to the Right seat? Has anyone else heard of this?

I have never personally had a Mesa jumpseater, but welcome aboard!