“Found in a library book. Tape over staples?”
This is an electro-magnetic security tag. So you can’t just take the book out without checking it out at the desk!
“I was cutting my watermelon and was confused when I saw these hard stems inside, does anyone know what they are?”
That happens when the watermelon gets stressed during growing. It was likely due to drought that the fruit got messed up inside. It’s technically edible, but likely doesn’t taste very good.
“A handle with 2 flat, crescent-shaped pieces of metal with corrugated edges, with the concave parts facing each other.”
It is for cutting wontons or dumplings.
“Found this in a public park. Everything not screened in is removable. What is it for?”
It’s a bee and bughouse filled with different materials for lone bugs to overwinter.
“What is this plastic rack used for? Stands about 3 ft high.”
This is a boot rack!
“What is the purpose of the metal plates on the ground in front of these water fountains?”
It is for blind people and their white cane. It is similar to the warning dots on the footpath at intersections.
“Found these in my cooked spaghetti. The sauce was canned.”
They definitely look like rosary peas. Don’t eat that spaghetti bro! And if you already ate it, go to the doctor.
“I bought a used guitar and it came with this plastic pouch which has a pick inside and this other thing. It’s too short to be an extra string.”
My guess is that it is an extra string for a different instrument (probably a ukulele). You mention that you bought the guitar used. If it was purchased from a music shop, they might have thrown that in so you had a pick and they didn’t really care about a random string. As a string instrument player, I have had plenty of little packets like that laying around.
“I have a long list of things that this is NOT — but I have no idea what it is.”
It is 100% a molinillo. Used in Colombia to make hot chocolate frothy.
“Found in my building’s recycling — Sailing / marine gear? Cat toy?”
It’s a flute embouchure trainer!
“Orange tape nailed to pavement with orange triangle and sometimes a number”
Surveyors control point. Surveyors will typically establish several control points just outside of the proposed work area that are a fixed location that will not likely change during construction. These points are usually GPS located and have a fixed elevation. It’s a way for the construction crews to have a way to verify that what they are building is located in the correct place and built to the right height.
“About the size of a ping pong ball, hollow like one too. Found in the woods.”
“Purchased these herbs in Hong Kong for soups and drinks, but don’t know what they are exactly.”
Kind of looks like Dendrobium.
“What is this bubbly stuff coming out of this banana? It split open by itself, like it’s under pressure.”
Ripened bananas tend to foam due to the presence of sugars.
“My old roommate forgot this in a kitchen drawer when they moved out, what is it?”
Bradshaw Good Cook corn stripper.