A fun little list of common TILs I see on this sub...

...because I'm chronically online

• you can, indeed, put a hat on your cat/dog/horse/child/alien scarecrow
• you have to manually pull hay from the hay feeder and place them on the trough to feed your coop and barn animals until you get the deluxe versions
• put water in your pet's water bowl. There's no penalty for not doing so, but it builds friendship faster.
• you can feed your horse a carrot to make them go very slightly faster for that day
• buy a workbench from Robin and make it touch every chest that contains crafting materials. You're welcome
• hold press and run around touching your animals to pet them all in one click
• hold a big chest and touch a regular chest to turn that chest big (I could have worded this better)
• long press when using your updated hoe and watering can to cover more squares in one go
• that icon on the upper right side of your inventory will pulse if you hover over an item needed for the community center
• there's also an "add to existing stacks" icon on the side of the inventory when you open a chest
• use the tab key to scroll through layers of your inventory (on PC)
• if you don't want kids, you can ask Robin to remove the crib from your house
• you can change the name of your animals anytime
• you can hatch slimes anywhere in the game, not just in the slime hutch
• you can put torches on sprinklers and fences
• if you chop down a fruit tree or tea bush, you'll get the sapling back

Additionals:

• check out the replies for lots more helpful tips
• if you so desire, you can change your farmer's gender in the wizard's basement
• you should probably try dropping a staircase in the mayor's house
• if you plant mixed seeds, you will sometimes see a seedling that looks like a wilted crop. It's not a wilted crop.
• fiber seeds grow in every season. You can use it to plot your crop layout in winter and have the tilled and watered soil ready for the first day of spring. Just make sure to plant 7 days(?) before the end of winter for a spring 1 harvest.