hehe... yeah... I think the sticker is like a temporary tattoo... Rupert was trying to be a bit more like his free-minded brother Rudy and he thought the tattoo would do the trick.
The most visible sign of ageing is the slight discoloration in his eyes, though.
P.S.: I checked on Rudy, too... he lost his eyes, though... might need a transplant ;)
Alright, I remember Rockin' Rudy! Would be a shame if he went blind...
Yeah, one of Rupert's eyes looks off, didn't notice that till you mentioned it :)