The observer, Jim Young, made the following interesting note about a star imaged in scan 070 on this night:

"looked like bright flash in frame #183 (+/-) in the K band
 only!  It was a point source...not moving!  It seemed to be
 at the same position of a star as it moved upwards during the
 telescope scan.  Check this out!"

During quality review of this night, the star in question was identified as IRAS 21095+6145 at J2000 coords 21h10m43.23s +61d58m19.3s. This star was identified as the correct match to the observer's description due to some unusual solo zapping seen in its halo at Ks band.

The individual images for frames 178, 179, 180, and 181 are shown, with J band in the first row, H in the second, and Ks in the third. IRAS 21095+6145 is the brightest star in each frame. Note that its appearance at J and H remains constant in these three frames, but the star appears to undergo an extreme brightening at Ks in frame 180 only.

Close-ups (all to the same scale) of frames 179, 180, and 181 at Ks show that despite the "brightening" of the star in frame 180, the diffraction spikes have not grown larger in response to that brightening. This indicates that the "brightening" took place after the star light had passed through the telescope optics and is most likely a detector artifact of some sort. The pixel at the center of the star's image in frame 180 happens to be a dead/bad pixel that is already masked.

Gene notes that the bad pixel is located at (x,y)=(182,80) with the center of the star probably being located slightly closer to (x,y)=(182,79):

Davy,
        Very close. The following is a pixel dump of the position of the
source in k frame 180 (r2-r1 less background):

  000703n/k070:
         76    77    78    79    80    81    82    83    84    85
 186:    554   640   806   793   693   656   571   403   NaN   163
 185:    568   818  1022  1538  1513  1079   694   493   346   209
 184:    586   963  2064  7436  4570  2240  1011   594   416   259
 182:    698  1506  9749 55640   NaN  5320  1279   626   408   275
 181:    584  1104  2738 27659 24293  2968  1323   749   419   287
 180:    391   646  1246  2413  3794  1751   840   718   494   235
 179:    373   515   638  1144  1183   889   815   520   421   269
 178:    258   350   372   591   632   610   584   477   286   209

the source was probably slightly closer to the center of 182/79.

gene

The results from Mike Skrutskie's subsequent investigation:

I've taken a look at frames 179 (no flare) and 180 (flare)
at different stretches.  It looks as if the star is the same
brightness in both frames, but what is different in the "flare"
frame is the halo around the star.  The operator sees the images
on a tight stretch, so the halo would look like saturated
pixels and thus give the impression of a very bright source.
I find it hard to conceive of an electronic means of producing
a halo.  The pixels are well isolated and don't bleed flux
for saturated stars.  Diffusing electrons radially and
symmetrically seems unlikely.  

On the other hand, a speck of dust on the substrate (of which
there are many) might just produce a halo of scattered light.
A raw flat field image might reveal such a dust speck at this
location.

Mike.

Because of the masked pixel in Ks frame 180, that extraction was automatically removed from consideration, and thus the photometry output for this source by the pipeline is correct.

Hence, we believe that this is an unusual artifact of the detector and/or electronics and is not, regrettably, interesting astrophysically.