When Judith is being fed the sandwich from Arby's you can see that the bun switches back and forth between a sesame seed bun and a kaiser bun.
When Judith is putting J.T.'s face in the toilet, in one shot he is wearing sheer black pantyhose over his face and in the next three shots he is wearing a fishnet stocking.
Darren calls out "B-17" as a bingo number, but bingo "B" columns only go up to 15.
When Wayne shoots the mother raccoon, it shows her lying on her left side with the dart in her right leg. The next time she is shown, she's lying on her right side and the dart is in her left leg. Most likely, the camera was flipped.
When Judith has a handcuff on her ankle, she apparently puts on a pair of shorts.
When Wayne and J.D. send the doctored photographs of Darren to Julia, the city, state, and zip code on the envelope read "Seattle, WA 21709". 21709 is the zip code for Frederick, MD. Any zip code in the Seattle area would begin with a '9'.
When Coach jumps out of the moving truck and is rolling in traffic, the dolly he is laying on can be seen.
When Darren and Sandy emerge from the water, they are nowhere near where they went into the water, as the background is totally different, the bridge seen from the pier not visible from the beach despite all the shots facing in the same direction.
Wayne claims that he was born at the "Hot August Night" concert. But the concert that is shown is not that concert. Hot August Night was recorded in 1972, and the concert that is shown is "Love at the Greek" recorded in 1976. (Also a mistake in Directors commentary, Dennis Dugan admits that the concert is not Hot August Night, but claims the concert that is shown takes place in 1974).
When the coach come to the guys house he dips an onion ring in dipping sauce and picks up and beer, Then he puts the beer down to pick up the remote and still has the onion ring in his hand and in the next shot he the beer in his hand that the controller was in and the controller in the hand that was just holding the onion ring.
When JD & Wayne are in Judith's office trying to negotiate her not seeing Darren anymore, She sets a timer telling them they have "2 & a half minutes" & shows the timer displaying at 2:28 & counting down. The timer goes off at around 1 minute & 20 seconds, not 2 & a half minutes.
During several of the chase scenes at night, you can see lights from police cars which are, apparently, blocking traffic while the scene is being filmed.
When Darren is thrown off the pier by Sandy, as it cuts to him stating he can't swim with his head above water, you can see a pair of feet going under the water. Presumably the stuntman's, who is just holding his breath and underwater.
The film is set in Seattle, Washington, but filmed in British Columbia, Canada. Not a problem in itself, except that the Lions Gate bridge in Vancouver is plainly visible as our heroes jump off the pier.
When Sandy agrees to have dinner with Darren, they go to The Cannery Seafood House. The scene in which Sandy throws Darren into the water was shot just outside the restaurant. Then, after Sandy jumps in to save Darren, they both walk up on the east end of Jericho Beach, near Jericho Tennis Club. The actual distance between the restaurant and Jericho Beach is approximately 8 miles!
The tux Darren is wearing at the end of the movie is not the same one he was wearing at his near wedding to Judith. It seems unlikely he would go out and buy/rent another one.