  For 3 radio-loud $\gamma$-ray detected Narrow-Line Seyfert 1 ($\gamma$-ray
NLSy1) galaxies, we report optical variability on intra-night and/or week-like
time scales, based on five $\geq$ 3 hours long monitoring sessions for each
galaxy. The radio-loudness factors (R$_{1.4 GHz}$) for these galaxies, namely
1H 0323$+$342 (z = 0.0629), PKS J1222$+$0413 (z = 0.966) and PKS J1505$+$0326
(z = 0.408) are $\sim$318, $\sim$1534 and $\sim$3364 at 1.4 GHz, respectively.
For the most distant $\gamma$-ray NLSy1, PKS J1222$+$0413, Intra-Night Optical
Variability (INOV) characterisation is presented for the first time. The
blazar-like behaviour of the nearest $\gamma$-ray NLSy1 1H 0323$+$342, which
showed strong INOV on 4 of the 5 nights, was unexpected in view of its recent
reclassification as `radio intermediate' (R$_{5 GHz}$ $\lesssim$ 25). Its
particularly violent INOV is manifested by two optical outbursts lasting $\sim$
1 hour, whose rapid brightening phase is shown to imply a doubling time of
$\sim$ 1 hour for the optical synchrotron flux, after (conservatively)
deducting the thermal optical emission contributed by the host galaxy and the
Seyfert nucleus. A more realistic `decontamination' could well reduce
substantially the flux doubling time, bringing it still closer in rapidity to
the ultra-fast VHE ($>$ 100 GeV) flares reported for the blazars PKS 1222$+$216
and PKS 2155$-$304. A large contamination by thermal optical emission may, in
fact, be common for NLSy1s as they are high Eddington rate accretors. The
present study further suggests that superluminal motion in the radio jet could
be a robust diagnostic of INOV.
