"Smart Alec"?

This English phrase (and the similar “clever clogs”) came up in another thread, and I wondered how you’d express it in colloquial Welsh.

Dictionaries and google didn’t help too much, but I did find

“Ffôn clyfar” for “smart phone”. So would “Alec clyfar” work in Welsh?

Or do people just go into Wenglish and say “smart Alec” (or its slightly ruder equivalent)?

(I must listen out on the soaps for this I think).

Diawl glyfar! or Mistar gwybod popeth!

I’ve just found them here: