Gilligan’s was the downstairs bar behind Thumbs and the DQ. Wasn’t there a fish store above it or close by?Your description fits my memory.
I thought "Under Where?" was earlier, lower level of the plaza where Co-Op Records used to be - then eventually was called Gilligan's. But maybe I'm confusing the two.
Underwhere was the downstairs bar under People’s, with the entrance on Lincoln Way.