Mike's place at the Hufflepuff table is dictated not by his year, or the proximity of any new friends he's made in his house, but by where Raphael is seated at the Gryffindor table. Mike always seems to find a spot at the Hufflepuff table just across the aisle from his brother, and usually spends most meal times straddling his seat so as to involve himself in as many conversations as possible.
Ye Olde Hufflepuff Table
The Hallowe'en feast appears to be no different.