Evolution Marches On: The asari have been largely successful as a spacefaring race, but eventually they have to realize that parthenogenesis is an evolutionary dead-end. It's theorized that within 5,000 years - that's only five generations for the species - the asari civilization will completely collapse from cultural stagnation. Cue Lina Vasir, daughter of Tela Vasir whose genetic mutation made her the first documented asari to exhibit sexual dimorphism (read: a male asari). Too bad 'she' was also a Ardat-Yakshi.
Fortunately, they found another male Asari later who was still in childhood and spirited him away, unofficially adopting him into the Spectre Clan after his mother died from the Batarians' Synthetic Plague. This led to a Crowning Moment of Heartwarming with Dempsey, and later confused the crap out of Madison when 'she' went to the boy's restroom.
Uncanny Valley: Practically a staple of the Spectre Base's residents is to be so used to strange things happening that almost nothing is too weird for them for more than a few minutes, before they accept as a normal occurence.