Carlin. I've not exactly been quiet about my opinion of Carlin in the past. I'll just leave the FAQ section here, and say burn his stuff with fire.

If you've represented what Carlin said about those two incidents accurately, then I have to say that while those events are attested, he's got quite an imagination.

Both are taken from Plutarch; the Scipio incident from the Moralia and the Cato one from the Life of Cato the Younger.

Here's the passage from the Moralia:

when he [Aemilianus] arrived at Alexandria and, after disembarking, was walking with his toga covering his head, the Alexandrians quickly surrounded him, and insisted that he uncover and show his face to their yearning eyes. And so he uncovered amid shouting and applause. The king could hardly keep up with them in walking because of his inactive life and his pampering of his body,​ and Scipio whispered softly to Panaetius, "Already the Alexandrians have received some benefit from our visit. For it is owing to us that they have seen their king walk."

There's nothing here about Aemilianus forcing the king to do anything, and nothing about Aemilianus wanting to discover if the king could walk; only a private quip to his companion.

The king in question was Ptolemy VIII Physcon. I wouldn't categorize him as a client king at all. Egypt was still the main power in the East (and would remain that until the battle of Actium in 31 BCE). As a matter of fact, Aemilianus had been sent to Egypt in part to get a feeling for its wealth and military power.

Is this story true? I don't know how Plutarch, writing something like 200ish years later, knows about a private joke Aemilianus made to his companion. I do know Panaetius was a Stoic philosopher, wrote his own stuff, and became the head of the Stoic school in Athens. Apparently his work was still in circulation in Cicero's time, and we have fragments of his student Posidonius' work. We have some titles of others of Panaetius' books, one titled On Cheerfulness that Plutarch seems to have had his hands on, so that might be a candidate.

As for Cato, Carlin is being a bit more scatalogical fanciful here.

There's a lot of political stuff going on in the background to this story. Ptolemy XI Alexander II supposedly left a will giving the Egyptian kingdom, including Cyprus, to Rome. He got himself expelled in 80 BCE, and reinstalled by Sulla, and quickly assassinated.

To get Cato out of Rome, Clodius passed a law making him governor of Cyprus. Cato knew what was up, but went anyway and hung out on Rhodes while his lieutenant tried to convince... I've lost track of my Ptolemies - some Ptolemy to surrender the island peacefully. Meanwhile, Ptolemy XII Auletes, who succeeded Ptolemy XI, got himself kicked out of Alexandria and turned to Rome for help (which he eventually got). On his way to Rome he wanted to talk to Cato. Cato was sick at the time and said Ptolemy could come to him.

Ok, now we get to the incident.

And when Ptolemy had come, Cato neither went to meet him nor rose from his seat, but greeted him as he would any ordinary visitor and bade him be seated.

The word for "rose from his seat" is ὑπεξανίσταμαι, which the LSJ defines as "arise" or "rise as a mark of respect for...." Nothing about a toilet.

Is this story true? Given the importance of the inheritance of Egypt held for Roman politics at the time, it's much easier to believe a story of what is essentially a diplomatic faux-pas survived for Plutarch to use when he wrote his life of Cato. On the other hand, Plutarch himself tells us he's less interested in facts than he is in giving an impression of character, and it is fitting with Cato's character to be overly stern.

Is it unusual for senators to act this way toward foreign royalty? Not at all. The senate often settled succession disputes, as they did with Numidia, settling the dispute between Jugurtha and his half-brothers (at first by politics, and later by war). For instance, earlier, after Punic 2, Gaius Popillius Laenas was sent to prevent a war between the Seleucid empire and Egypt. The king of the Seleucids at the time was Antiochus IV Epiphanes. This is what Livy says:

After crossing the river at Eleusis, about four miles from Alexandria, he [Antiochus] was met by the Roman commissioners, to whom he gave a friendly greeting and held out his hand to Popilius. Popilius, however, placed in his hand the tablets on which was written the decree of the senate and told him first of all to read it. After reading it through, he said he would call his friends into council and consider what he ought to do. Popilius, stern and imperious as ever, drew a circle round the king with the stick he was carrying and said, "Before you step out of that circle give me a reply to lay before the senate." For a few moments he hesitated, astounded at such a peremptory order, and at last replied, "I will do what the senate thinks right." Not till then did Popilius extend his hand to the king as to a friend and ally.

Is that true? Again, diplomatic stuff. Seems not unreasonable to think that story could survive until Livy incorporated it into his history. But either way, these stories show there's a Roman ethos of disregarding kings. It's how they want to think they act, even if they don't act that way in reality.