hi i am just wondering, this may be a silly question but i have never had an entire dog before they have all been castrated. when my dog gets a little excited(and stiff) he seems to have what appears to be two sets of testicals one that you can obviously see and the other set arrives when like i said he gets "excited" is this normal or should i take him to the vets. thanks for any replys.

This is perfectly normal. What you can see is the 'bulb' of the penis (castrated dogs have it too!) which swells on arousal. Nothing to worry about.
:)