A4
: 
This is what I found on another site:
YOSHI's RABBIT LOCATION
1 Outside the castle, right at the end of the bridge
2 Outside the castle, right at the end of the bridge
3 Outside the castle, right at the end of the bridge
4 Outside the castle, in a patch of flowers to the right
5 Outside the castle, at the bottom of the drained moat
6 Outside the castle, to the left among the maze of hedges
7 In the basement, in front of the entrance to Lethal Lava Land
MARIO's RABBIT LOCATION
8 Outside castle, left of the bridge
9 Outside castle, at the bottom of the moat (after it's been drained)
10 Inside the room with the entrance to Jolly Roger Bay
11 In the basement, in front of the entrance to Lethal Lava Land
12 In the basement, in front of the entrance to Lethal Lava Land
13 On the second floor of the castle, at the very top of the stairs
14 On the second floor of the castle, in the room with the large mirror wall
LUIGI's RABBIT LOCATION
15 Outside the castle, to the left among the maze of hedges
16 In the room with the entrance to Bob-Omb Battlefield
17 Behind the castle, in the courtyard with the boos (backflip right outside the doorway)
18 In the basement, in the room where you drain the water from the moat
19 On the second floor of the castle, just right of the doorway
20 In the room with the entrance to Sunshine Isles (behind the Rec Room)
21 Outside the castle, on the roof (you need 150 stars to unlock the cannon)
WARIO's RABBIT LOCATION
22 Outside the castle, to the far right
23 In the room with the entrance to Whomp's Fortress
23 In the basement, in the left hall with the mushroom guy
25 Behind the castle, in the courtyard with the boos
26 On the second floor of the castle, in the halls with the entrance to Tiny-Huge Island
27 On the third floor of the castle, near the entrance to Tick Tock Clock
28 On the third floor of the castle, in the upper alcove to the left