Despite how simple it is to pick up a banana in DKCR, there's an incredible amount of work that goes into the effect. Naturally the feedback for this action is highly polished, since you'll be collecting hundreds (if not thousands) of bananas every single level. But as complicated as the effect seems, it's actually just several simple moves layered on one another.
No matter where the banana starts, the collection effect finishes in a blazing 0.4 seconds (12 frames). Despite all the effort that goes into this effect, it exists simply to tell the player they collected a single banana. Players are here to play as Donkey Kong, not a banana accountant or effects afficianado. So get out of the way!
The banana UI updates immediately on collection - NOT when the banana finally reaches the UI. While the latter makes sense "physically", any delay in feedback risks confusing the player. Since the UI updates immediately, it reinforces that, yes, you did do something by touching the banana! Even though the effect is very fast (0.4 seconds), it's still too long for feedback.
After a banana is collected, it displays three images instead of one. Each image has varying opacity, with the "leading" image having the lowest opacity, and the center image having the highest. This is an incredibly simple (and inexpensive!) way to make the banana feel more fluid when moving. (It's worth noting that the trail renderer matches the opacity of the banana it's behind).
Once collected, each banana picks a random trajectory with which to enter the UI. Because DK is often stationary when collecting bananas, the random trajectory reinforces you're collecting multiple bananas at once. Without this, the bananas would quickly blend into a single, unified stream.
The banana enters Donkey Kong's UI instead of the Banana Count UI. Possibly because DK's UI is guarenteed to always be in the same place (assuring that bananas will never need to change course mid-way)? Or maybe because DK is the once actually collecting the banana, as opposed to the ethereal counter.
The particle that plays on collection is unusually large. That is until you put DK in front of the effect. He's a big, giant ape - so the particles expand to match the extra girth.
The bananas travel using a simple, two-handle bezier curve. This made choosing a random trajectory for takeoff simple, since all that needed to be defined was an angle for takeoff, while still traveling to the UI in a predictable pattern (the target handle is constant).