The famous boot scene is in "Wink of an Eye." There's no helpful screencap in this album (I don't have my disks at the moment, so I can't watch the episode to see if there's a helpful frame):
http://tos.trekcore.com/hd/thumbnails.php?album=77&page=39
http://tos.trekcore.com/hd/albums/3x11hd/winkofaneyehd1143.jpg
In this screencap from "Shore Leave," it looks like Kirk had white underclothing below his knees.
http://tos.trekcore.com/hd/albums/1x15hd/shoreleavehd608.jpg
http://tos.trekcore.com/hd/thumbnails.php?album=16&page=21
But I can't tell whether it's socks, long johns, or something else, like for the wrestling around. It kinda looks like white long johns tucked into black socks (assuming both legs are the same), but I don't know.![]()
Nice observation. Filming dates Oct. 19-26, 1966, which were warm days according to Weather Underground - highs upper 80s or 90s. Too warm for long johns, even in the morning.