I’ve been duped by red drip irrigation emitters, like this, thinking it’s a Num-Num Fruit (Carissa).
Another one that also confuses me are Spittlebugs (Aphrophoridae), which make spit-like formations on plants. For example, I’m still not sure if this one is a spittlebug or human.
Definitely spittlebug.
To me kind of the opposite has happened, one day I was walking through the woods and saw a bright red thing on leaf litter, so I thought it was a red plastic thing but when picked up, realized it was a seed of Erythrina standleyana!
BTW I planted that seed and it’s a sapling now hehe!
I had an experience like that at the Bronx Zoo. In the woodland I heard a bird going squeaky, squeaky, squeaky, but it turned out to be a woman pushing a stroller that needed oiling.
I think about this one a lot: https://www.inaturalist.org/observations/87465394
I really thought I had found some type of wondrous water creature that could boggle the (at least MY) mind.
I was listening to my swamp cooler on the roof just now, squeaking in a way that often suggests something is about to fail, only to discover it was a cricket just outside my door.
I’d rather be hearing rain than crickets tonight … about time to look for moths if it’s not too windy
I can’t count the number of sticks/bits of rope/funny shaped trash I’ve slammed on the brakes for…
I had something similar happen: a nondescript goose near a dock, stared at it through binoculars for quite some time looking for any field marks or other indication of species. Finally, I noticed that as it bobbed on the gentle waves, its head and neck stayed perfectly rigid. Decoy.
who hasnt been fooled by a decoy bird? i know i have
unrelated, one time i was on a trip and staying in a little place right on the beach, and the beach was super exciting to me - shells absolutely everywhere, couldnt step anywhere without stepping on many shells. even though it was terribly cold by my weak, floridian standards, i enjoyed going to the beach every night at like midnight and observing everything that caught my attention until my hands were too numb and then id start making my way back.
i found a sponge!
https://www.inaturalist.org/observations/36340073
Oh yeeah, I just saw a giant grasshopper some minutes ago!!! Let me see it with my binoculars… IT’S A STICK!! Noooo! I’ve been tricked today!
This just happened like five minutes ago.
Outside Badlands National Park near Wall, South Dakota, USA, is an infamous statue of a Mountain Goat on the cliff outside a private residence. We photographed it so proudly and then the next day it was still there and hadn’t moved…
In the US and Canadian interior West, our family devised a term and acronym for all the Black Bear lookalikes formed by fallen trees/stumps: Stumpy Moss Bear (SMB).
At work, we have a cabinet of curiosities, odd things that we’ve picked up during fieldwork. It’s mostly animal bones, pine cones, and weird rocks. There is a lumpy, patterned gray object that looked sort of like a sea urchin test. I was curious about it one day so I picked it up and turned it over and on the bottom, it says “Titleist.” It sat out in the desert sun so long that the covering disintegrated and the shape sort of slumped into a blob.
There’s a statue of a tiger on a hill in central NM, posed among the junipers, that has likely fooled some folks. It was pointed out to me one day and I photo’d it but have not posted to iNat.
That’s so insanely realistic! Look at it’s pose!
Shortly after making this observation, I was on travel and walked across the parking lot of my hotel to grab some dinner. It was dusk, and I thought I saw a large mushroom in the lawn. Imagine my disappointment upon realizing that it was not another Ganoderma, just a discarded hamburger bun!
Haven’t we all seen the observations on iNat of polyester batting that someone hoped was mammal fur or plant down?
Haha, this is an illusion, just like the scarecrows that the farmers put up in the rice fields, and the birds will think they are people when they see them.
I’ve never put a scarecrow but I honestly don’t believe birds are that dumb I mean, they can even recognize human faces, why won’t they recognize a scarecrow as just a scarecrow if it doesn’t even move?
You won’t believe how many times I have jumped back before realizing the snake I “avoided” was a stick. Or a piece of rope. Or I was walking along and something whacked the back of my leg, only to realize that I’d been bitten by a “stick snake” because I stepped on one end of a stick, causing the other end to whoosh up and whack me on the leg.
There are a lot of stick snakes around here. 
Although there are also a lot of real copperheads and rattlesnakes and two of our dogs have been bitten by copperheads - one a week ago and one yesterday - so I’d rather jump away like a fool when I see something that looks like a snake than be a real fool and get close enough to be bitten.