SOSO LALA is German and is almost an onomatopoetic term for "Nobody is overly excited" mostly used ironicaly.
The SOSO LALA poster is never wrong for friends who can take a joke and go trough life with a healthy amount of irony. It always looks good in the alley or in the kitchen of those friends.
As we all know a silly jokes never hurt anybody. Right? Riiight??