Is type not extended...

I'm not proud of this, and am not certain if it works on all platforms or will with future updates but interesting non-the-less...

'Returns a pointer to a class for a given object 'obj'
Function GetClassForObject:Byte Ptr(obj:Object)
	Local objPtr:Int Ptr = Int Ptr((Byte Ptr(obj)) - 8)
	Return Byte Ptr(objPtr[0])
End Function

'Returns a pointer to the super-class of a class pointed to by a given pointer 'class'
Function GetSuperClass:Byte Ptr(class:Byte Ptr)
	Return Byte Ptr((Int Ptr(class))[0])
End Function

'Returns the name of a class pointed to by a given pointer 'class'
Function GetClassName:String(class:Byte Ptr)
	If Not class Then Return Null
	Local debug_scope:Int Ptr = Int Ptr((Int Ptr(class))[2])
	Local szClass:Byte Ptr = Byte Ptr(debug_scope[1])
	Return String.FromCString(szClass)
End Function

'Returns the name of the class for a given object 'obj'
Function GetClassNameForObject:String(obj:Object)
	Return GetClassName(GetClassForObject(obj))	
End Function

'Returns TRUE for an object 'obj' that has a super class named 'className', otherwise returns FALSE
Function IsInstanceOf:Int(obj:Object, className:String)
	className = className.ToLower()
	Local class:Byte Ptr = GetClassForObject(obj)
	While GetClassName(class).ToLower() <> className
		class = GetSuperClass(class)
		If Not class Return False
	Wend
	Return True
End Function

Implementing your function is as simple as...

Function IsThisJustABob:Int(i:Bob)
	Return GetClassNameForObject(i) = "Bob"
End Function