I totally know that digital clock effect you're talking about. It's caused by something else though. It's actually a physiological hallucination due to high power ultrasonic waves coming out of those types of clocks. Rather than smoothly turning a small crank at 60rpm like in an analog clock, the clockwork gnomes inside digital clocks have to frantically push and pull a lever at 32.768KHz, and their stiff little pointy silk hats make perfect tweeter elements. It's also why those clocks get so warm, and why the snooze button is so unreliable; the gnome gets a well deserved nap, but is so exhausted he sleeps through his own alarm...
Oh... What? Hallucinations from a 32kHz RTC? Can't tell if your entire comment is a joke or just the last half... Couldn't find a thing after a quick search but now I'm curious.
I can certainly perceive all those flickering effects when moving the eyes. Slow PWM is hell, but some stuff like colour separation can be cool too.
My favourite trick is making a digital clock's numbers "slide" over the clock's surface, in a sort of parallax way. I guess that's due to low refresh rates, so for a very brief moment there's a disconnect between the clock's physical position and the last know position of the digits.