There’s a store in Berkley, MI which specializes in nostalgia items. The place is called “Time Travelers” and their lot has signs saying “Parking for Time Travelers Only.”
There is the town motto for Biggar, Saskatchewan:
Circa 2000 there was a web humor site with parody text for a real airlines safety placard — you know, those cartoonishly drawn instructions on what to do in an emergency.
The funniest panel was rewritten: “Passengers with Eighties hairdos will be tossed into the ocean.”
They didn’t consider “Biggar is Better”?
Sign for Gotham England:
Not that I’m aware of. 
I’m not even going to link to another motto that got changed a while ago.
I think it was a National Airlines pilot giving the pitch:
“Once airborne the flight attendants will require anyone detected smoking to deplane immediately”
An effective warning sign:
All personnel are required to shower before reporting for work. If I have to kiss your ass to get you to do your job, I at least want it to be clean.
A friend swiped a placard from a commercial fishing boat and gave it to me. I hung it on our most recent pontoon boat. It read something along the lines of: “Any injuries occurring on this vessel must be reported to the captain in a timely manner”.
Guests on the boat often read and reread the sign, but nobody ever questioned it. It looked “official”.
When I sold the boat the sign remained.
More stupid than humorous, but randomly I get a huge warning on my trucks display about taking eyes off the road to use that system. This happens while I’m driving.
You have to take your eyes off the road to read that warning, and you have to take a hand off the steering wheel to press the “ok” icon.
I have seen this pseudo-German warning in a few electronics shops.
Achtung: Das machine ist nicht fer gerfingerpoken und mittengraben. Ist easy snappen der springenwerk blowenfusen, und corkenpoppin mit spitzensparken. Ist nicht fer gewerken by das dumpkofen. Das rubbernecken sightseeren keepen das hands in das pockets. Relaxen und watchen das blinkenlights
I like to peruse despair.com every so often. This is probably my favorite.
I’ve seen that one before. Reminds me of “Gellarese”.
Dublin Zoo?
Dunno if the National Park Service actually used this or if only exists on the 'Net.
