Kled's name resembles Welsh noun cledd(yf) /kleːð(ɨv)/ "sword", from Proto-Celtic *kladiwos
Kladiwos might have been loaned into Latin as gladius, or both come from same PIE root *kelh₂- "to strike" (compare Brand's Pyroclasm)
Skaarl is from a species called drakalops, immortal, unkillable wind spirits that embody the desolation of the Noxian Plains.
Kled's posters call Skaarl the 'pride of Noxus' and a 'decorated veteran of the battle of Bucket Creek', with the drakalops' gender changing depending on the poster; Kled knows that Skaarl is female, yet unaware of the posters' conundrum.
Kled and Skaarl are the first champion with two health bars, combining to form the highest in-game base health, with Kled's being the lowest as well as having no level growth.
Kled is the first champion to swear (albeit censored) in-game.
Kled is suspected to be (as) old(er) as Noxus itself (by extension a contemporary of Poppy's).
Kled's military contributions (Battle of Fallgren, Battle of Bucket Creek, Battle of Drugne, Siege of Rugg, Siege of Qualthala, Assault on Glorft, Sacking of Trevail, Draken Campaign, and most recently the Ionian Campaign) might have been what turned Noxus from a tribal confederation into the empire it has become.
Kled is the most distinguished military person to ever live, although most of his titles are made up and/or self-proclaimed.
Kled's 'mushroom juice' may be derived from the ones Teemo uses for his traps.