I did the "evil circus tent of illusions" bit in 3e.
5th level party. Bad guys were just two wizards, one a child, two special zombies. And lots of illusions.
They had encountered a cleric who was headed back to town. He and another had been charged to build a shrine at a wilderness ford. His friend vanished in the night.
They find a big circus tent about 1.5 miles from the unfinished shrine.
Great fun. They were actually tense, "frightened".
Who can forget the fun...
The PC wizard attempting to drop a Potion of Fireball (house rules, as a grenade) down the illusory bottomless pit at his feet.
Them assuming the interior was tardis-like and solid, when it was all illusions. They killed two of their own horses, tied up outside, with a Fireball. They were confused by the area of effect spells appearing to go through the walls. They were confused by the Lightning Bolts from nowhere.
It took the potion/explosion damaging people who thought they were a long way away to start to clue them in.
The discomfort as the mostly male party was invited into the fountain pool by two male lovers, who kept trying to flirt with the Ranger.
The shock and horror on realizing that the two male lovers in the pool were actually a (house rules special) zombie of the cleric they were searching for...and an 8 year old evil wizard prodigy girl.
But I didn't use clowns.
Next time it has to have clowns.
Maybe Hostages. Illusioned as Evil Clowns. (Ok, that is evil)