Some time in the early 90s Goro Shimura was giving a lecture course on algebraic number theory at the ENS in Paris. According to someone who was in the audience, one of the lectures started thus.
Let $a$ be a rational number. [Pause; the lecturer writes $a$ on the blackboard.] Is this clear? [Pause.] Do you follow me? [Long pause.]
Ok then. [Pause.] Let $\beta$ be an irrational number. [Pause; the lecturer writes $\beta$ on the blackboard.] Is this clear? [Pause.] Does everyone understand? [Long pause.]
Ok then. So consider a global field of prime characteristic and an automorphic representation of an algebraic group over its adelic ring. Now take the absolute Galois group and the category of perverse l-adic sheaves on ...
[The third phrase here is a random and probably inaccurate reconstruction, but I'm pretty sure the numbers were called $a$ and $\beta$.]
upd: I've emailed the person I heard this from and they provided the following version. It seems that I got everything wrong; apologies. Anyhow, the course took place at Jussieu, not ENS and began thus.
Consider alpha algebraic number, writes alpha on the blackboard, pause
(on the same line) now theta transcendental number, writes theta, pause
(below the first line) f holomorphic function, writes f, pause
(on the same second line below theta) g non-holomorphic function,
writes g, pause
long silence which I interpreted as "think deeply about the meaning of
Professor Shimura takes a deep breathe and in one sentence restarts:
Let f be a Siegel modular form of weight k and level N ....