Average humanoid height in the Galaxy was somewhere between two and two-and-a-half meters.  The nine Guardians were all an identical height of 124 centimeters.  They also had filtrums.

Filtrums are rectangular clefts in the skin leading from the bridge between the two nostrils to the middle of the upper lip.  Most of the humanoids in the area of the Central Cluster had them.  The only known incidences of filtrums in humanoids outside that region of the Galaxy were on the planets Earth and Krypton.  There were several theories on the reasons for this incidence of the apparently functionless birthmark, but one thing was known about them.  Only humanoids with filtrums were capable of smiling.

The youngest of the Guardians was born within twenty years of the oldest, roughly eight billion years ago.  Their blue skin was completely unwrinkled, they no longer had visible pores or prints in their skin, they each had a fringe of thick white fur around the sides and backs of their heads, they were virtually identical in appearance.  What active communication they had with each other was instant, on a subliminal level.  They no longer had any need for telepathy.  Their functions were identical, their aspirations and jealousies were lost to the ages.  Only one Guardian had actually left Oa in eight billion years, and he returned only briefly to be stripped of his immortality as punishment for some subtle breach of the group's ethical code.

Somewhere in the labyrinthine tunnels and towers and interconnecting halls of the Guardians' headquarters on the otherwise barren planetoid, two of the immortals were communicating.

Our wayward brother has located and induced a dream sleep upon the Earthman, the first Guardian told the second.

Is he equipped to feed tomorrow's experiences into the mind of the Terran? the second inquired of the first.

He will be, by the time our evaluation of his interview with the woman arrives at Earth.

The second Guardian passed his hand over a light on the wall as a spotlight from the ceiling bathed the first Guardian's head, feeding information directly into the immortal's mind.

The light went off as the Guardian integrated the information and noted, I believe you have done a good job, but I have one possible improvement.

Might I consider it? the second suggested without apprehension.

The point at which the woman Lane asks, Have you ever tried to talk a mugger out of pursuing his vocation, Professor Gordon?

Yes, where the man Gordon responds, I haven't had the opportunity, thank the stars.

Exactly.  It is with the response that I have a question.  Perhaps he could respond with an attempt at levity.  For example, God parted the Red Sea for Moses, the Colonials beat back the British Empire, the Mets won the pennant in '69, and a mugger can be talked down, Miss Lane.

That is quite in keeping with the Terran penchant for light humor, and I considered such a response, but I determined that in Professor Gordon's case it would be out of character.

I concede to your superior acquaintance with the subject.  I shall begin to feed the experience into the young man's somnolent mind.  He will believe himself to have been functional during this entire period.