After beating the Normal Staff Ghosts by a certain margin of time, you can unlock the Expert Staff Ghosts. The following are the approximated times for unlocking them:
Mario Kart Wii
Mushroom Cup
Luigi Circuit
Normal Staff Ghost Time: 01:29.670
Unlock Time: 01:25.742
Expert Staff Ghost Time: 01:19.419
Luigi
Moo Moo Meadows
Normal Staff Ghost Time: 01:37.856
Unlock Time: 01:33.571
Expert Staff Ghost Time: 01:25.909
Baby Daisy
Mushroom Gorge
Normal Staff Ghost Time: 02:16.110
Unlock Time: 02:07.755
Expert Staff Ghost Time: 02:01.011
Toadette
Toad's Factory
Normal Staff Ghost Time: 02:22.480
Unlock Time: 02:17.469
Expert Staff Ghost Time: 02:05.593
Toad
Flower Cup
Mario Circuit
Normal Staff Ghost Time: 01:44.777
Unlock Time: 01:39.183
Expert Staff Ghost Time: 01:33.702
Mario
Coconut Mall
Normal Staff Ghost Time: 02:30.764
Unlock Time: 02:25.160
Expert Staff Ghost Time: 02:13.333
Daisy
DK Summit
Normal Staff Ghost Time: 02:34.693
Unlock Time: 02:25.907
Expert Staff Ghost Time: 02:17.546
Donkey Kong
Wario's Gold Mine
Normal Staff Ghost Time: 02:19.585
Unlock Time: 02:15.301
Expert Staff Ghost Time: 02:04.800
Wario
Star Cup
Daisy Circuit
Normal Staff Ghost Time: 01:56.822
Unlock Time: 01:52.791
Expert Staff Ghost Time: 01:41.362
Daisy
Koopa Cape
Normal Staff Ghost Time: 03:03.022
Unlock Time: 02:54.897
Expert Staff Ghost Time: 02:41.370
Koopa Troopa
Maple Treeway
Normal Staff Ghost Time: 02:58.633
Unlock Time: 02:50.229
Expert Staff Ghost Time: 02:37.812
Diddy Kong
Grumble Volcano
Normal Staff Ghost Time: 02:28.237
Unlock Time: 02:21.190
Expert Staff Ghost Time: 02:11.852
Dry Bowser
Special Cup
Dry Dry Ruins
Normal Staff Ghost Time: 02:30.949
Unlock Time: 02:24.927
Expert Staff Ghost Time: 02:14.286
Yoshi
Moonview Highway
Normal Staff Ghost Time: 02:16.802
Unlock Time: 02:10.093
Expert Staff Ghost Time: 02:04.163
Peach
Bowser's Castle
Normal Staff Ghost Time: 03:04.836
Unlock Time: 02:55.017
Expert Staff Ghost Time: 02:42.098
Bowser
Rainbow Road
Normal Staff Ghost Time: 03:05.895
Unlock Time: 02:59.293
Expert Staff Ghost Time: 02:44.734
Rosalina
Shell Cup
GCN Peach Beach
Normal Staff Ghost Time: 01:34.233
Unlock Time: 01:30.698
Expert Staff Ghost Time: 01:23.140
Peach
DS Yoshi Falls
Normal Staff Ghost Time: 01:16.461
Unlock Time: 01:13.589
Expert Staff Ghost Time: 01:09.175
Yoshi
SNES Ghost Valley 2
Normal Staff Ghost Time: 01:06.595
Unlock Time: 01:03.752
Expert Staff Ghost Time: 00:58.907
King Boo
N64 Mario Raceway
Normal Staff Ghost Time: 02:14.799
Unlock Time: 02:07.915
Expert Staff Ghost Time: 01:59.053
Baby Mario
Banana Cup
N64 Sherbet Land
Normal Staff Ghost Time: 02:48.651
Unlock Time: 02:37.784
Expert Staff Ghost Time: 02:28.356
Baby Luigi
GBA Shy Guy Beach
Normal Staff Ghost Time: 01:45.568
Unlock Time: 01:39.255
Expert Staff Ghost Time: 01:32.867
Koopa Troopa
DS Delfino Square
Normal Staff Ghost Time: 02:41.807
Unlock Time: 02:33.107
Expert Staff Ghost Time: 02:24.169
Wario
GCN Waluigi Stadium
Normal Staff Ghost Time: 02:32.882
Unlock Time: 02:24.645
Expert Staff Ghost Time: 02:12.367
Waluigi
Leaf Cup
DS Desert Hills
Normal Staff Ghost Time: 02:10.233
Unlock Time: 02:01.141
Expert Staff Ghost Time: 01:52.686
Dry Bones
GBA Bowser Castle 3
Normal Staff Ghost Time: 02:58.304
Unlock Time: 02:52.637
Expert Staff Ghost Time: 02:39.391
Dry Bowser
N64 DK's Jungle Parkway
Normal Staff Ghost Time: 02:58.264
Unlock Time: 02:49.028
Expert Staff Ghost Time: 02:37.782
Donkey Kong
GCN Mario Circuit
Normal Staff Ghost Time: 01:59.771
Unlock Time: 01:55.267
Expert Staff Ghost Time: 01:49.939
Mario
Lightning Cup
SNES Mario Circuit 3
Normal Staff Ghost Time: 01:38.880
Unlock Time: 01:34.828
Expert Staff Ghost Time: 01:26.659
Baby Mario
DS Peach Gardens
Normal Staff Ghost Time: 02:34.894
Unlock Time: 02:29.006
Expert Staff Ghost Time: 02:16.777
Baby Peach
GCN DK Mountain
Normal Staff Ghost Time: 02:57.744
Unlock Time: 02:50.248
Expert Staff Ghost Time: 02:38.130
Funky Kong
N64 Bowser's Castle
Normal Staff Ghost Time: 03:19.323
Unlock Time: 03:06.723
Expert Staff Ghost Time: 02:55.933
Bowser Jr
Mario Kart 8
| Course | Character | Body | Tires | Glider |
|---|---|---|---|---|
| Mario Kart Stadium |  |
 |
 |
 |
| Water Park |  |
 |
 |
|
| Sweet Sweet Canyon |  |
 |
 |
 |
| Thwomp Ruins |  |
 |
 |
|
| Mario Circuit | |
 |
|
|
| Toad Harbor |  |
 |
 |
 |
| Twisted Mansion |  |
 |
 |
|
| Shy Guy Falls |  |
 |
|
|
| Sunshine Airport |  |
 |
|
|
| Dolphin Shoals |  |
 |
|
 |
| Electrodrome |  |
 |
|
|
| Mount Wario |  |
 |
|
 |
| Cloudtop Cruise |  |
 |
|
|
| Bone-Dry Dunes |  |
 |
|
|
| Bowser's Castle |  |
 |
|
|
| Rainbow Road |  |
 |
|
|
| Wii Moo Moo Meadows |  |
|
 |
|
| GBA Mario Circuit |  |
 |
|
|
| DS Cheep Cheep Beach |  |
 |
 |
 |
| N64 Toad's Turnpike |  |
 |
|
|
| GCN Dry Dry Desert |  |
|
|
|
| SNES Donut Plains 3 |  |
 |
|
 |
| N64 Royal Raceway | |
 |
|
|
| 3DS DK Jungle | |
|
|
|
| DS Wario Stadium |  |
|
 |
|
| GCN Sherbet Land |  |
 |
|
|
| 3DS Music Park |  |
|
|
|
| N64 Yoshi Valley |  |
 |
|
 |
| DS Tick-Tock Clock |  |
|
|
|
| 3DS Piranha Plant Slide |  |
 |
|
|
| Wii Grumble Volcano |  |
|
|
|
| N64 Rainbow Road |  |
 |
|
|