You can unlock a Cheat called 'Play as a dog!' then enable it in the secrets menu!
Nintendo 64 location:
Go to the maximum security cell in the Gardelle county jail after you kill the fat boss find the hole to drop down. Open the security gates. The cell is the one farthest to the left.
Go to the Asylum: Gateway and go to the path before the door on the left under the bridge. Follow it until finding a room with a Govi and some boxes. Climb the boxes and jump on the rafters. Jump to the second rafter, then jump to the third r
after. The "Secret Activated" message will appear.
PC and Remastered Location:
Louisiana Swampland - Exit the church and on your left is a square raised platform, use the calabash to drop down and obtain the secret! Woof!