Yes, the original reference is not Portal. I don't even know what Portal 2 looks like not being a gamer, but the spaaaaace reference is much older than Portal 2 and possibly older than the people that created Portal 2.
In the final scene of Portal 2, a robot that was obsessed with going to space [1] drifts across the background and interrupts the villain, screaming "spaaaaaace!" out of excitement for finally being in space. The Portal usage is probably not related to the Lost/Pigs in Space usage.
