I've only come across two REALLY clown greens over the years. A hole in Cape Coral that appeared to set by a newbie in the false front of a green. Totally inappropriate spot that WAS fixed after a few groups went though. The other was at the 12th at Great Rock on LI. Shortest par 3 on the course. I hit a great wedge right at the pin in the back right of the green, ball landed and bounced once just missing a hole in one. Ball stopped then started rolling back, just missing the hole again and wound up on the fringe at the front left of the green. The other guys hit balls to the green and all wound up landing and rolling down into the same area. Putts back to the hole were a useless endeavor- they ALL wound up coming all the way back down to the front.
Sure, there have been LOTS of greens that were quick and I paid the price by being above the hole and over cooked the putt back down, but rarely have I seen greens that were joke worthy. Although, there is ONE green that always give people grief. On the Green at Bethpage, there is a hole that appears to have an elephant buried just on the left edge of the green, and they will SOMETIMES put the hole near the mound, but never actually on it. You can approach the putt normally from almost every direction. You also will NEVER have to putt down or across the mound- it's that steep so the ball will never stay on it. Worst feeling is possibly hitting a great approach just to the left of that position and have it carom off the elephant somewhere. There is a usually a bet of $10- If, you are less than 2 feet away from the hole- either putting towards the mound or away from it, you may putt up the elephant and back down to the hole. If it goes in you're $30 richer, if not add an EXTRA stroke for the hole. So if you're putting for par, miss the elephant shot then tap in, you take a 6. If you make it- you get your 4 and $30. Sometimes it's doubled for birdies.