Euribor Flipper??

the citibank trade you are referring to occirred early in August last year.
The spike in bobl in dec (around 27 i think) was unrelated to the citibank trades...

Basically Citibank bid up the bunds and bobls - this raised the pirce of the cash equivalents.
Then they sold around 200 cash Euro bonds on MTS... before buying a chunk back half an hour later

The Decemeber thing with Bobl was in a very thin market between xmas and new year. Phily Fed ( i think it was) came out at 5pm London time, it was a very good number. No size in the market a lot of shops closed for holidays and basically stops went off. It recovered almost immediately.