Actual character cameos in Starbreed are unlikely, but there might be some easter eggs.
If there was to be any cross-over/cameos, it would be more likely that SpunkStock hosts a character from Starbreed. (Though I will clarify that there are no plans for this, just that if it were to ever happen, that would be a more likely scenario. SpunkStock just seems like a more suitable game for such things)
Glad you enjoyed! ^^