One question, isn't krypto part of the current continuity of Superman? If he is, when did he come around?
As dto explains above, the answer is "yes" and he first showed up in the Return to Krypton storyline. He's been in a few scattered issues since then, mostly those written by Jeph Loeb.
One way to differentiate between the original Krypto and his modern incarnation is that the new one has an S shield dog tag, which the original never had:
