@tsarstepan,
Hard to say, with the exception of Tony the tiger, the bloke on the Quaker oats packet and the cock on the cornflakes box mascots were transient.
I remember Sugar Smacks had a procession of Jerry Anderson and Star Trek characters on the packet.
I used to confuse Tony the tiger with the Esso tiger.
When I was a bit older the Honey Monster became very big as the mascot for sugar puffs, replacing a bear, the honey monster is so big it's now honey monster's cereal and no longer sugar puffs.
other than that the prospector from Golden nuggets and Doc from Wheatos are the only ones to last.
we do get American cereals over here, (things like Chix and Lucky Charms, not Kellogs which has been over here for a very long time) but only very recently, and as they're imported they're very expensive.