Ds2 (7) stole ds1's (9) best Dr Who card, took it to school and traded it! (And ultra-rare one!) Then claimed he'd found the card on the playground at school.
Needless to say we have had serious words.
I was really shocked though as to how long he persisted with the lies. What fun!
(DS1 doesn't tell lies and doesn't really understand the concept. He believed ds2's web of lies completely, and was astonished to discover the truth. ... and not best pleased either.)