The Ghost Survivors DLC comprises of 4 new stories, each containing at least 1 Mr. Raccoon to shoot. You can play on any difficulty to earn these. They are as follows:
[0:03] - No Time to Mourn 1
[0:26] - No Time to Mourn 2
[0:40] - No Time to Mourn 3
[1:18] - No Time to Mourn 4 *
[1:33] - Runaway 1
[1:51] - Runaway 2
[2:15] - Runaway 3
[2:37] - Forgotten Solider 1
[2:56] - Forgotten Solider 2
[3:16] - No Way Out 1
*Note: No Time to Mourn 3 and No Time to Mourn 4 are on different paths at the end, meaning they cannot be grabbed in the same run. No Time to Mourn 4 is on the short/dangerous path.