Ever since the Princess of Wales surfaced publicly Monday near Windsor -- being photographed in a car driven by her mother, wearing sunglasses and seemingly trying to lay low -- the internet has kicked off a fresh round of jokes, memes and conspiracy theories.

Fact is ... people saw these pics, and a lot of them just aren't convinced it's really her -- even though we know for a fact it is. And yet -- Twitter's having a field day regardless.

Hop online and you'll see exactly what we're talking about -- a lot of these posts are clearly done in jest and all in good fun ... but it's unfortunate they're making light of a serious sitch.

Some are simply throwing out other examples of stars pap'd from the inside of their cars over the years and comparing those to Kate's new shots. Some of the names that are being juxtaposed to KM ... Britney Spears, Michael Jackson, Lindsay Lohan, just to name a few.

However, some are taking this a little more seriously ... picking apart the pictures that surfaced yesterday and getting into the details of her face, including moles/dimples, etc.

These folks are suggesting the woman photographed Monday really isn't Kate ... pointing out that specific features of hers aren't there for whoever was in the car (again, it was obviously her).

Some think they see her sister, Pippa, here ... some see a totally different person entirely.

Like we said ... it's all a bunch of nonsense and tomfoolery -- and, TBH, it's just the Internet being ridiculous ... which is what it was already doing even before this latest sighting.

The Palace has said Kate is continuing to recover from her abdominal surgery in January -- and word just came down Tuesday that she won't actually resume her duties until June.