One of the academic panels at Renovation was "The Boundary Beneath: A Glimpse at Underwear in Speculative Literature and Film". The presenter was Dr. Sharon D. King, who showed film clips and stills of scenes showing actors in their underwear, and then lectured about what it meant. According to my notes, actors could be portrayed in their underwear:
1. to titilate
2. to show loss of status
3. to show rebirth
4. to show humiliation
5. to show vulnerability
Among famous film "underwear" scenes are:
Sigourney Weaver in white cottons in Alien (1979)
Brad Majors and Janet Weiss being invited to Dr. Frank-N-Furter's laboratory in Rocky Horror Picture Show (1975), and
Kelly LeBrock's character Lisa in Weird Science (1985)
I think showing actors in underwear can also represent depravity, or just emphasize the beauty of some human bodies - for example, in Lady Gaga's Telephone *.
But what can we make of SpongeBob SquarePants, who lives in Bikini Bottom and who says things like "I'm wearing three pairs of underwear right now."? Maybe "actors in underwear" has become a cliche?
*In which Dr. Stern has a bit part. She is not just an academic. She writes fiction and non-fiction, and she is an actress.