Resulting alternate postulations necessarily involve the sudden mass-extinction of one species, almost immediately followed by the magical and/or miraculous introduction of a new species - homo sapiens - by the creationist's deity of choice, be it God or aliens.
Despite the fact that this "theory" cannot hold up to a tiny fraction of the rigor they grace the theory of evolution with, proponents of intelligent design often fervently insist that the "missing link" in the chain of evolution is undeniable proof that the theory of evolution is entirely unfounded, and that their highly unlikely postulate of intelligent design must be the only logical solution.
In reality, the "missing link" represents but one piece of missing evidence among millions of pieces of existing evidence for evolution. This can be contrasted to the almost complete lack of any evidence whatsoever for the proposed alternate theory of intelligent design, as well as the willful ignorance of any physical evidence that does in fact exist (which is commonly dismissed by arguments such as "LOL THE DEVIL PUT IT THERE").
The field of psychology explains that this type of reasoning has its roots in a phenomenon known as the "confirmation bias", which is the tendency of a person to seek out and interpret information which enforces their predrawn conclusions and reject information which challenges said conclusions. The confirmation bias can be found at the heart of many junk sciences in which conclusions are drawn before any physical evidence is gathered to lead one to that conclusion.
Creationist: It's the missing link! The answer must be Intelligent Design!