Lu is from a German child program (“Der Maus” I believe it’s called). Next to this A319 there is also A321 D-AIRY featuring a mouse.

“Der Maus” is a program explaining stuff. And in one of their episodes they explained how planes where made. The two planes they used to explain it where A319 D-AILU and A321 D-AIRY.

Initially the planes flew in the regular livery. But after a lot of letters where send in by kids, LH decided to honour Lu and “Der Maus” on the airbusses featured in the program.

Not quite right.

Lu is the symbol of the Lufthansa child program.

The mouse (Die Maus) is on D-AIRY is there because htis german childrens TV program (Die Sendung mit der Maus) had been fllowing that plane from the cutting of the first metal to the first flight with Lufthansa and had devoted on series to that aircraft.

There is no direct connection between both symbols.