Freud's first line, when he is bewildered by the Phone Booth's presence: "This is a dream?" Dream interpretation is a key tool in psychoanalysis, which Freud created.
Joan sees the Phone Booth appear in front of an altar while she was praying. She probably thought Bill and Ted were angels there to take her to heaven. Note that the real Joan of Arc claimed to have talked to angels.
Lincoln acts surprised when the camera flashes as he's getting a portrait. In Lincoln's time, photography required a long period of calibration and the subject standing perfectly still. He no doubt was startled that the picture was taken instantly.
Billy's casual demeanor and smirk when he is being interviewed by the San Dimas Police. He'd been to jail a few times at this point in his life, and escaped every time. Surely he was confident he could do it again.
Napoleon gets into "Waterloo" (a stealth pun on its own) because he walks through the turnstile in the middle of a group of kids. Napoleon has a famous (though untrue) reputation for being short.
Socrates is understandably astonished at the first few stops he makes with the group, but none more so than the brief trip to the future... where they arrive in a palace-like structure with metallic walls and a group of robed figures seated on floating thrones. He must have thought they had traveled to the abode of the gods on Mount Olympus!
After misidentifying Joan of Arc as "Noah's wife", Bill and Ted wonder aloud "Then who was Noah's wife?" This is actually a very good question in itself, because (like many Biblical wives) she is nameless in the text, having few identifiable qualities beyond being the wife of Noah.
The movie lampshades the illogical nature of time-paradox causality loop from the start:
```Bill:``` ... Wyld Stallyns will never be a super-band until we get Eddie Van Halen on guitar. ```Ted:``` Yes, Bill, but... I do not believe we will get Eddie Van Halen before we have a triumphant video. ```Bill:``` Ted, it's pointless to have a triumphant video before we have decent instruments. ```Ted:``` Well, how can we have decent instruments if we don't really even know how to play? ```Bill:``` That is why we need Eddie Van Halen! ```Ted:``` And that is why we need a triumphant video! ```Both:``` [think for a second] EXCELLENT! (guitar riff)"
The dialogue parallels the inherent problem in the time-loop:
To do their history report, Rufus had to help them For Rufus to exist, Bill and Ted had to do their history report Bill and Ted did their history report and Rufus helped them with their history report
Joan of Arc, Abraham Lincoln, Billy the Kid and Socrates were all executed or murdered, yet Bill and Ted happily send them back to their own time in the end. One wonders whether the boys did enough studying to even find out about the grim fates awaiting many of their new friends.
In one of the comics, Bill and Ted discovered that Abraham Lincoln was murdered shortly after they returned him back to his time after the end of the film. They went back to stop it and it ended up changing history in a poor way. After they corrected the change they made, Death informed them that Abraham ended up in Heaven and is happy there, learning that Death is an inevitable and a part of life (be it the past or the future). But, if that's not of an explanation for everyone else, you can use the below.
They know they're all dead. Bill himself clearly knows this, as when asked about who Napoleon was at the start of film, his only response was, "He's dead." To which the teacher responded, "So, you're telling me that history is full a bunch of old, dead dudes?" Since the past is the past, Bill and Ted both know that they're no longer alive in their time, and they understand that is how life is.