Okay.. I think this fixes it all.

code/modules/surgery/organs/organ_internal.dm

@@ -218,7 +218,7 @@
 				LI = new()
 			LI.Insert(src)
 			if(only_one)
-				return
+				return TRUE
 
 		if(has_stomach && !getorganslot(ORGAN_SLOT_STOMACH))
 			var/obj/item/organ/stomach/S
@@ -229,19 +229,19 @@
 				S = new()
 			S.Insert(src)
 			if(only_one)
-				return
+				return TRUE
 
 	if(breathes && !getorganslot(ORGAN_SLOT_LUNGS))
 		var/obj/item/organ/lungs/L = new()
 		L.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(blooded && !getorganslot(ORGAN_SLOT_HEART))
 		var/obj/item/organ/heart/H = new()
 		H.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(!getorganslot(ORGAN_SLOT_TONGUE))
 		var/obj/item/organ/tongue/T
@@ -254,7 +254,7 @@
 		// if they have no mutant tongues, give them a regular one
 		T.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	else if (!only_one)
 		var/obj/item/organ/tongue/oT = getorganslot(ORGAN_SLOT_TONGUE)
@@ -278,7 +278,7 @@
 			E = new()
 		E.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(!getorganslot(ORGAN_SLOT_EARS))
 		var/obj/item/organ/ears/ears
@@ -289,7 +289,7 @@
 
 		ears.Insert(src)
 		if(only_one)
-			return
+			return TRUE
 
 	if(!getorganslot(ORGAN_SLOT_TAIL))
 		var/obj/item/organ/tail/tail
@@ -297,4 +297,4 @@
 			tail = new dna.species.mutanttail
 			tail.Insert(src)
 			if(only_one)
-				return
+				return TRUE