How do I make a SOC object

[nukedude01]

I'm trying to make just an MT_THOK reskin but with the sprite being DODOB0. This is what I have so far:
FREESLOT
MT_DODO
S_DODO

Thing MT_DODO
Mapthingnum = -1
Spawnstate = S_DODO
Spawnhealth = 1
Radius = 32*FRACUNIT
Height = 64*FRACUNIT
Flags = MF_NOBLOCKMAP|MF_NOCLIP|MF_NOCLIPHEIGHT|MF_NOGRAVITY|MF_SCENERY

Frame S_DODO
Spritename = DODO
Spriteframe = B
Duration = 8

Yet it doesn't work. At all. I have the sprite in the /sprites directory of the PK3, and I've already converted it to the SRB2 palette. However, when I run it I get an error saying "CANNOT FIND SPR_DODO".

 

[Honey Bee]

you have to freeslot the sprite, just type SPR_DODO

 

[cheeseboi.]

you have to put SPR_DODO in the freeslot

 

[nukedude01]

you have to freeslot the sprite, just type SPR_DODO

you have to put SPR_DODO in the freeslot

Thanks y'all