It's no wonder Bill S. Preston Esq. and Ted Theodore Logan make such great pals. They have nothing but openness and enthusiasm for everyone they meet. But even more than that, they are almost the exact same -- to borrow their terminology -- dude.
We can imagine Wayne and Garth going their separate ways. Cheech and Chong have personalities that are distinct enough that solo adventures also do not seem like much of a stretch. Even Beavis and Butthead have their own characteristics. But separate Bill from Ted and their characters lose all definition. Not since Bob and Doug McKenzie have two parts of a duo depended so heavily on one another for entertainment value.
But Bob and Doug were brothers. What's Bill and Ted's story? How does their relationship function? Are there any particular traits we can attribute more to one than the other? How does the mysterious and fickle Missy... I mean Mom fit into all of this? Such queries provide the aim for this completely superfluous and boneheaded academic exploration.
In a figurative sense, Bill and Ted appear to share the same brain. Naturally, it is not possible for two separate humans to share the same brain organ. But one can be forgiven for using the phrase here as it seems true in all but the most physical sense. Bill and Ted do not dress identically. They did not arrive from the same genetic pool (Or do they? -- foolheaded speculation to come). And yet they display near identical personalities including an overabundance of altruism, underdeveloped learning abilities and shared cultural priorities. Most famously, they possess a remarkable ability to intuit each other's thoughts and speak in unison without apparent preparation. Even more bizarre, they are capable of emitting harmonious guitar phrases from their hands merely by wiggling their fingers at the same time.
Bill and Ted come from different households, raised by fathers with very different parenting styles. Bill's dad seems intellectual and easygoing, but also less interested in Bill's affairs. Ted's dad rules with an iron-fisted discipline. Tellingly, neither Ted nor Bill has a mother in his life. Perhaps their similarities come from having the same mother. This conjecture may sound farfetched, but we do witness their fathers’ swapping Bill and Ted’s former classmate, Missy, from one film to the next, so the theory does contain some precedence. Assuming they had the same mother and noting her absence whether by death or abandonment, we begin to understand the complexity and emotional importance of Bill and Ted's unity, especially in the face of such lacking domestic male role models.
But they were not always together. And some things do separate them. For instance, Ted has a little brother, Deacon, whose social life appears quite typical compared to Ted's. When the duo experience their own personal Hells in Bill and Ted's Bogus Journey, they share one (military school) but suffer their next in solitude. Bill flashes back to his scary grandmother's birthday kiss, while Ted deals with guilt (manifested in a maniacal Easter Bunny) over stealing candy from Deacon. The experiences which shaped who they are were not shared.
Furthermore, careful viewers will note some distinctions in Bill and Ted's personalities. In Excellent Adventure, we find Bill much more cautious in general than Ted (though Ted does seem to take over this trait somewhat in Bogus Journey). Excellent Adventure also establishes Ted as the duo's expert when it comes to ladies.
But beyond that, we find very little difference in the two men. However they grew up, they have no hesitation living together as adults. And even when it comes to outside domestic affairs, they appear unified, as seen when Bill and Ted propose to the Medieval Babes in privacy yet give almost identical speeches, both of which end with "Will you marry us?"
This extreme unity goes even further than that. Throughout their adventures and journeys, we see multiple forms of Bill and Ted -- evil robot form, good robot form and future form. All display the same level of equality. Note that when Bill and Ted meet their future selves in Excellent Adventure, they become more like quadruplets than a pair of twins. Interestingly, the series' only actual set of twins, the extraterrestrial scientist, Station, can merge its two halves into a greater whole when necessary. Bill and Ted do not have this power. They instead expand outward, remaking the world in their image through the power of music, extreme positivity and strangely large vocabularies.
But I am not certain they are friends. Their pathological dependency on one another suggests something far less voluntary. To see what true friendship looks like in the Bill and Ted universe, look no further than the bromance which blossoms between Billy the Kid and Socrates, two abducted travelers who could not be more different and yet manage to find harmony with each other. Perhaps they represent the first manifestation of the way that proximity to Bill and Ted's abnormally close relationship makes friends of us all.