Monica interviews for a job with Phoebe's client Steve, who plans on opening a restaurant. She cooks him dinner and Rachel is their waitress. In The One with the Blind Dates (2003), Rachel goes on a "blind date" set up by Phoebe, who turns out to be Steve, even though Rachel met him years earlier. However, it was not a real blind date as Phoebe was not legitimately trying to find her someone but was trying to motivate her to reunite with Ross.
Ross makes a comment while watching TV that proof evolution is just a theory. But shortly after, in The One Where Heckles Dies (1995), he vehemently argues with Phoebe that evolution is undeniable fact.
When Ross and Joey are sitting in Joey's kitchen, the antenna behind Ross's head appears and disappears between shots.
When Monica is making dinner for Steve, he finds a pack of taco shells. On the right side of the screen, you can see Rachel gesturing her arm toward him, and then in the next shot she gestures toward him again.
When Phoebe is in Chandler's office, they look out of a half-size window, but at the external view it is a full size window. There is a wall that comes up 3 feet at most before the window begins. During the external shot, the camera is looking up at the FROM that same wall. The window has not changed sizes, we just cannot see the wall from the external angle.
It is clear that when Chandler, played by Matthew Perry, is sitting at his desk in the cubicle just before Ms. Peblock arrives, he's simply typing away at the keys in the center of the keyboard, and not really working at filling in data on his computer.
At the 6:41 mark, when Ross's date Celia is leaning over and Marcel is hanging from her hair, there is clearly a third human present. On the right side of the screen is a blond male with a mustache momentarily leaning in, almost certainly Marcel's (Katie's) handler.