Family resemblance...

When Pentax jumped into the mirrorless interchangeable lens camera craze in 2011, it's pretty obvious from where they drew their styling inspiration.

The Pentax Auto 110 of the late-'70s and early-'80s was pimped as the tiniest interchangeable lens SLR on the market, using the little 110 Instamatic film cartridges Kodak had introduced in '72.

Pentax marketed the Q-series digitals the same way. Ironically, the teeny 110 film negatives are the same size as a Micro 4/3 image sensor, which is much larger than the little 1/2.3" sensor chosen for the initial Q models. (The later Q7 and Q-S1 had slightly larger 1/1.7" sensors.)

From Wikipedia.

The small sensors are going to cause problems with noise at higher ISOs...

click to embiggenate

The above image is using the 3.2mm f/5.6 03 fisheye lens on the Q-S1, which has the later, larger sensor. It's a 1/6th second exposure at ISO 3200 and is obviously noisy as dammit.

Despite being an interchangeable lens camera, the Q-S1 uses the same 1/1.7" sensor size as my late, lamented Coolpix P7000, a higher-end compact. (The original Q and the Q10 use a smaller sensor, the same size as the one in the old Canon ShowerPot SX500 I've since handed off to Bobbi.)
.