First on screen appearance of Dan Povenmire and Swampy Marsh, creators of Phineas & Ferb.
This aired as part of the "Time Shift" marathon along with "Excaliferb" and "Phineas and Ferb and the Temple of Juatchadoon".
It's unknown if the Chinese Candace, Linda and Lawrence are related to Phineas and Ferb because they were never seen interacting with them.
The main universe Phineas and Ferb don't appear in either episode segment, but their prehistoric and Ancient Chinese counterparts do.
The Candace of the Chinese timeline is trying to bust Phineas and Ferb because, as according to her, the technology the boys use to make their big ideas is far too advanced for their time.