The dimensional messing-about is far deeper than we expect.The original Tony is not the one from earlier in the storyline, he's from a dimension close enough that he didn't notice any differences. The dimension is not the one from earlier in the storyline but rather a dimension close enough to Original Tony's and Greg's that they don't notice. Tony was originally both evil and apathetic and was temporarily replaced by a less apathetic alt-world self that built the space shuttle and original Tony is back, or any combination of the above. The entire world could even have been destroyed as a result of the plot hole, and the loophole was not a fix'd portal, but rather an entirely new universe created by Tony's idea in the world outside of being. And, just to put the final nail in the transdimensional packing crate, the teleporter works like the time machine referenced from Timeline, sending people to an alternate dimension that is fifty miles to the left as the time machine would send one to a similar universe that exists 4 years earlier than ours. Every time the characters go somewhere and don't return through the same teleport door, they've trapped themselves in a dimension further and further from their own.
WMG / Real Life Comics