(First of all, this is originally the idea of @Dogleader , I am merely continuing the "series". I don't want to take credit for making these posts, thank Dogleader for originally coming up with this idea of making an informative post.)
Rambi is a helpful Animal Friend, having been the second-most recurring Animal Buddy, behind Squawks the Parrot. He is a large rhinoceros tough enough to smash boulders blocking his way. In the early days, he was often helpful for finding hidden Bonus Rooms by smashing certain walls. Rambi is also known to bash through hoards of enemies without taking damage-although the player should avoid bashing through enemies on fire.
In the first Donkey Kong Country game he could be found in Rambi Crates, which were usually easy to spot. He makes his debut in the first level, Jungle Hijinx, where both Bonus Rooms need to have their entrances cleared by ramming into them with Rambi.
The successor to DKC, Donkey Kong Country 2: Diddy's Kong Quest, introduces a new chargeable attack. By holding 'A', and releasing it a few seconds after, Rambi charges in a straight line, smashing everything in his path. However, Rambi needs to use the new attack if the player still wants to clear entrances to Bonus Rooms.
Next, Rambi makes several cameos in spin-off titles, but he wouldn't reappear in a main game until Donkey Kong Country Returns. Here, he can still bash through enemies with ease, although he doesn't smash walls anymore, and his chargeable attack is gone. Diddy Kong can make his jumps a bit longer, although the effect doesn't last as long as without Rambi.
His last recent appearance was in Donkey Kong Country: Tropical Freeze, where he functioned exactly as in the game's predecessor.