As John Brownlee explains in his article Quimps, Plewds, And Grawlixes: The Secret Language Of Comic Strips for fastcodedesign.com, Plewds are the beads of sweat that drip off of characters in comics. This term was coined by Mort Walker who is famous for his comic strips, Beetle Bailey, Hi and Lois, and his book The Lexicon of Comicana.
Plewds further, are the “drops of sweat that spray outwards from a cartoon character under emotional stress,” (Brownlee). In the frame from Flex Mentallo, the man is clearly nervous, so to show this, a massive amount of plewds are expelling from his body. The same can be said about Jon from Garfield, he is clearly under a lot of pressure so plewds are falling quickly from his body.
According to Brownlee the more plewds the character has, the more upset he, she, or it is. Typically the plewds come off of the characters face. I like to think of these as sweat beads because that is basically what they are.
Another attribute of plewds is that they can vary based on what each character is feeling (Brownlee.)
If a character is relieved the plewds will be few, if a character is very stressed like Jon, there are a ton of plewds.
Lastly, in the Snappy Sammy Smoot comic by Skip Williamson, the character on the far right has a very small amount of plewds coming off his face.
Brownlee, J. (2013, July 15). Quimps, Plewds, And Grawlixes: The Secret Language Of Comic Strips. Retrieved October 1, 2015, from fastcodedesign.com.