Gundam Build Fighters is a fun series about people using Gundam model kits to fight each other, and it’s absolutely oozing with references to both popular and obscure parts of the Gundam franchise. In the last episode, the anime pulls out what I think is the best reference of all, especially given the concept of the show.
In the final battle against the (scale-model) space fortress A Baoa Qu, the characters work together to take down a common threat. Among these characters is the father of the protagonist Iori Sei. Having won the silver medal at a previous tournament using a model of the original Gundam, in this scene Sei’s father Takeshi brings out the Perfect Gundam.
Though it did get a Master Grade model kit a number of years ago, the Perfect Gundam is not the most well-known Mobile Suit in the franchise. Its relative lack of popularity, however, is less important than its actual origin. The Perfect Gundam is featured as the hero’s Gundam in the 1982 manga Plamo Kyoushirou, which is premised around kids using Gundam models to fight each other in virtual reality environments. In other words, the appearance of the Perfect Gundam is actually an homage to the spiritual predecessor of the Gundam Build Fighters concept, reinforced by the fact that it’s the father of the hero who is using it.