That's a breath of fresh air on a Monday. The theme is explained nicely at 61A: Babies (aww ...) ... or an aural hint to 18-, 32-, 39- and 57-Across (CUTIES). Each long answer is a two word phrase whose initials are QT. They're all solid phrases, although QUARTERTONE is a bit out there for a Monday theme answer. And are 36D: Actor's prompt (CUE) and 65A: Blow away (AWE) sneaky additional thematic material?
3D: Creature that attacked the Nautilus in "Twenty Thousand Leagues Under the Sea" (GIANTSQUID) and 29D: Italian blue cheese (GORGONZOLA) are really outstanding long down answers. I also enjoyed 4D: Tree whose name contains all five vowels (SEQUOIA), almost enough to make it my favorite answer of the day.
The rest of the fill is fairly strong. I never like UTAHNS, and ADEE and ETTE are the kind of glue Jeff Chen likes to say are necessary evils. There's nothing I really hated. I enjoyed AQUA/LUNG, even though it wasn't referring to the Jethro Tull song. GINNIE Mae fooled me: I wanted faNNIE, of course.
1A: Game in which to cry "You're it!" (TAG) is saved by the liveliness of the clue, so I'll give it a C+. And my favorite clue-answer pair was 22A: Band aide (ROADIE). I love the lack of a question mark, certainly not needed here.
Thumbs up from me.