99 Words About … Christopher Guest’s sublime ‘Family Tree’

Christopher Guest's sensibilities all over "Family Tree."

There are clues.

Michael McKean. The mockumentary style. A character so traumatized as a child by a self-pleasuring puffin, she can only express emotion through her ever-present monkey puppet.

But your first definitive proof that “Family Tree” (10:30 p.m. Sunday, HBO) is Christopher Guest’s comes with next week’s costume horse derby.

When the genealogy-tracing Tom (“Bridesmaids’ ” Chris O’Dowd) honors his British great-grandfather by racing in a two-person horse costume (don’t ask), it’s handled with such pomp and self-seriousness, it could only come from Guest.

The improvisational writer-director’s first output since 2006 proves he hasn’t skipped a perfectly timed beat.

— CHRISTOPHER LAWRENCE