Larson apparently used “Sylvia” and “Rhonda” as go-to names for his recurring gag archetype of ordinary, slightly ditzy suburban women who show up in absurd contexts.
There’s no single canonical “Sylvia and Rhonda,” those two names just recur across several different Far Side panels as stand-ins for that “unremarkable women reacting drolly to something bizarre” trope.
Anticomedy! Anticomedy! pitchforks
It’s a good premise just not believable which is why I give this panel 1 1/2 stars.
Edit: This is a Perd Hapley quote.