FN SIZE on a mini Cooper (appropriate plate for the car, for sure)
ORNGUBAD on a vintage rust-orange sports car of some description
XTS XTC on, well, an XTS
A little road trip this afternoon…
An SUV with EAZZZZY.
A Subaru Outback: WAVNSNW in a Mammoth Lakes frame. Clearly an all season boarder.
On an eleventh (who knew?) generation (2002-2005) Ford Thunderbird: 1TEEBRD. I don’t know if there’s a subtle golf reference in there.
And finally, on a Lexus SUV: IATRGNC. Iatrogenic, of course. Clearly a physician with a sense of humor.
ROR X84 on an Accord. Is ROR an abbreviation for something, and there are 84 of them? Or maybe their initials are ROR, and they were born in 1984.
RYS RAV4 on what else, a RAV4. I suppose it’s perhaps Ray’s RAV4, or some similarly named person.
LADYKAT on a black Lincoln SUV. I couldn’t see the driver. Maybe other variants of “cat lady” were taken?
Seen last night on a late-model Porsche coupe: GDIYUP.
Or maybe it’s “Lady Katherine”.
I’m now imagining a rather large cat speaking to another cat: “The car even says on the plate that a cat’s driving, and still the humans don’t notice!”
ONE ME
I don’t have any idea.
MR SLEEP on a Genesis sedan in the office parking lot. There was also a Sacramento Kings frame, probably unrelated but I thought I’d mention it just in case.
GDEEYUP on a Jeep Wrangler
RDSTER on a Cooper Mini
12 PAWS
SXSPEED on a Honda Accord. Sex speed? Or maybe a dyslexic version of excess speed? Probably not anything urological. 
Maybe he or she is a bicyclist with a six speed bike.
Probably “six speed”, as in a 6 speed manual transmission. Can you get one of those on an Accord? Off the top of my head I know the sporty-ish Civic Si comes with a 6 speed, as does the high performance Civic Type R. But I’m not sure if you can still get a manual Accord.
Six speed, of course! Apparently, do-it-youself shifting ended for the Accord in 2019. The car in question was clearly a few years old, so yeah.
A big Chevy Silverado pickup: MIONCA. No idea. If it helps, the rear window had a decal of an eagle holding a pair of assault rifles with the legend: In God We Trust - Guns Are Just Backup.
Perhaps MONICA was taken?
Or CAMINO
Here at the Chevy dealer, a C8 Vette with UGONE
CHWBACA on a Kia crossover. It was a sort of light metallic brown, so I wonder if Chewbaca is the car’s name.