The text is a play on the catchphrase 'I tawt I taw a puddy tat!' from the cartoon character Tweety Bird, with a twist incorporating the concept of assimilation from the Borg of the Star Trek universe. The humor arises from the blending of two distinct fictional universes and the alteration of the original phrase to include 'attimilated' (a play on 'assimilated'), which sounds similar to 'tawt'.
Tweety of Borg : I tawt I attimilated a Puddy Tat !