Preheat oven to 425°F.
Fill an ungreased 24 mini-muffin baking pan with three frozen tater tots per cup (they can be stacked loosely). Place the tray in the oven and bake for 15 minutes.
Arrange the bacon slices in a single layer on a sheet pan lined with parchment or aluminum foil and bake at 425° for approximately 13-15 minutes until they're deeply browned. Remove and drain on paper towels. Crumble into 1/4" pieces. (This step can also be done while the tot cups are cooling later.)
Take the tot cup tray out of the oven and place on the counter. With the back of a spoon (or your fingers if the tots aren't too hot), gently smash the tots so they fill each cup.
Using a plastic measuring cup from a medicine bottle (see recipe notes above), a small shot glass, or your fingers if neither of the other items is available, push down into the center of each cup to create a hollow cup with ridges. You can use your fingers to fix any uneven spots, pushing potato bits into place (they'll end up sticking to each other as they finish baking).
Place the tray back into the oven and bake for another 30-45 minutes until the cups are deeply golden. The crispier you can get them, the longer they'll hold up after filling.
While the tots are baking, make the filling: julienne the unpeeled apple into 1/8" matchsticks, then slice crosswise to create 1/8" dice (brunoise) and combine with sour cream, shredded cheese, and lemon juice.
When the tot cups are deeply golden, remove them from the tray and let cool on a cooling rack.
Remove the skin and pit from the avocado and cut into small dice (1/4").
Fill each cup with the sour cream mixture and top with avocado and bacon crumbles. You can easily transport the cups by putting them back into the mini-muffin tray and covering with foil or plastic wrap. Store any leftover sour cream mixture in the fridge for up to 2 days; you'll have frozen tots leftover anyway; might as well cook up a few more cups for yourself!