While scrolling through the reviews for CPP Pizza on YELP, I found a lot of reviews mentioning that there were very huge amounts of kids. I can't assess the relevance, so please see for yourself:

Then around 7 PM, all these kids came out of nowhere and it was hard to hit the ball without hitting one of them in the face!

https://web.archive.org/web/20161206224342/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=Ciuu_4iQNpIYr5D7lAuj2w&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

I am glad we sat outside because after we ate, we decided to go in to check out the atmosphere and ping pong tables (hopefully try to play a game), but there were children running around EVERYWHERE!! Don't get me wrong, I love children, I even teach, but these kids were running from their tables (where the parents were still sitting) to the ping pong tables and back like it was a relay race. It seemed as though there were 50 children, when in actuality, there were probably only 25, but still, I felt like I was in a classroom gone awry. The inside of Comet Ping Pong was a little TOO happening for us.

https://web.archive.org/web/20161206224237/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=l2jEOWofMLsWjqPM_iz95w&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

The atmosphere was also different than I expected. I thought that the pizza parlor was integrated with the game room. Instead, the back half of the restaurant had little kids playing ping pong, and the front of the restaurant was more of a beer bar for people in their 20s. The two areas seemed like entirely different places.

https://web.archive.org/web/20161206224009/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=j4mEhJGGFwK_Mr5xEIYQiQ&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

If you enjoy the atmosphere of Chuck E. Cheese with somewhat more upscale prices, this is the place for you. If you don't enjoy having other people's badly behaved children constantly fielding ping pong balls at your head and your food, this is probably NOT the place for you. I arrived expecting this to be a "Dave and Busters" style grownup fun and games place. And this restaurant is a good idea that, if properly executed, would be a lot of fun. The problem is that many parents treat this place like Chuck E. Cheese. Children run back and forth between the tables, hit ping pong balls wildly, and are allowed to roam, unsupervised. Neither the management or the waiters seemed particularly troubled by this, but I found it decidedly annoying.

https://web.archive.org/web/20161206222909/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=dztks5tyo3KZr3sCxWlIpg&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=%28direct%29

If Chuck E. Cheese were a hipster who smoked Crystal Meth, this would be the dining concept he would come up with. With an art deco style that can only be described as "phony dilapidated", this place bore a strong resemblance to Freddy Krueger's boiler room, except with much more metal structures that served no purpose. To put a fine point on the ambiance, there was a projector in the room playing extended video footage of a car tire on fire while spinning on a rope--so as to give that "family Italian" feel so commonly found in Pizza places. I waited to be seated at around dinner time and the place was packed. It had more crying kids than a hospital maternity ward. Apparently they must have been saddened by the motif of this place as well.

https://web.archive.org/web/20161206223455/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=c5gArbigr51pbjMR06rSKw&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

The place was OVERRUN with kids. I like kids, but I felt like I was drinking beer in the middle of a playground. Running around, screaming, completely monopolizing the ping pong tables, climbing on my chair (!!). It completely ruined the experience for me, unfortunately.

https://web.archive.org/web/20161206223612/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=14Gvi_UsW33fUpuLpMbcWQ&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

At first the place was great, ping pong in the rear, good beer on tap, and food in the front. Then the rear started to turn into a playground. at one point I counted in excess of 15 kids under 10 wanting to "play. Parents who couldn't understand why they couldn't "play". No wonder the paddles are all ruined. Seemed parents enjoyed hanging out the bar to drink while they sent their kids to the rear for unsupervised playtime.

https://web.archive.org/web/20161206223712/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=oxo0r63HZSygwn1wjzpMOg&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

This place, at least before 8, was KID CENTRAL! Seriously, we were trying our best not to step on the groups of sugar high kids weaving in and out of our legs.

https://web.archive.org/web/20161206224123/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=d4qdASphJ5XEOom1kZqjGg&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

However...I didn't realize that this place turns into Chuck-E-Cheese in the early dinner hours. HOLY SHNIKES that place was PACKED with little kids, and the ping pong area was a total zoo.

https://web.archive.org/web/20161206224428/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=tQpFJfbSjnFru_g4BNctgQ&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

It is incredibly friendly; the wait staff seemed to actually enjoy interacting with the kids.

https://web.archive.org/web/20161206224529/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=iGNnV1ovKaQzJr6-a1pE8Q&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

Unfortunately, the dinnertime atmosphere appears to be pretty lacking. There were approximately 9,000 little kids in there. If I'm going to spend 10 or so bucks on a personal pizza, I don't want to feel like I'm at Chuck-E-Cheese. I'll go back, but not before 8 pm. Beer list was great, although I didn't really feel like having a beer when the kids behind me were shaking my booth by playing some hand-slap game.

https://web.archive.org/web/20161206224615/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=qBH1rA1HQVvqSh-pjI0RaA&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

Although we arrived around 8:30pm on a Friday night, there were still too many young kids running than I would have liked.

https://web.archive.org/web/20161206224722/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=hLgkj8yUfJm9LpRkSgwV0w&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

down sides? too many kids, like the parents love to find the ping pongs tables to keep their kids busy while they can get drunk. So.. ping pong lovers..... please don't disappoint yourself by expecting any serious ping pong here.

https://web.archive.org/web/20161206225020/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=THkQi8nyzCNa_lQGHFX2fQ&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

 

Various other cites from the "Not recommended" section of YELP (https://www.yelp.com/not_recommended_reviews/comet-ping-pong-washington)::)

I have been in port-a-potties that were cleaner and smelled LESS of urine than the one at this place.

Families let their kids go screaming wild in the ping pong area while the parents eat in the other room. Don't venture in the kids room as it is intense and frightening

Chaotic (uncontrolled and undisciplined children),

Additionally, the ping pong portion of the restaurant is entirely unregulated, so if you go on any weekend day, expect to find a herd of children dominating the tables for hours at a time.

Ping pong was fun, but extremely difficult to play with adults not watching their kids run under/around/ and INTO the tables while other adults are playing.

----- I have not made backups of every page of the "Not recommended" section, so if you find anything in this section please archive and post it -----

 

I also found mentions of a hidden door, but this seems to be just the toilet door (?):

Had a great time. I tried this place because of a deal from SalesVote and it was awesome, the pizza was bomb. Insightful tip: Head towards the back, on your right is a small room with beer cages. Push against the wooden wall there, which will reveal two hidden doors.

https://web.archive.org/web/20161206223820/https://www.yelp.com/not_recommended_reviews/comet-ping-pong-washington?not_recommended_start=80

Image that seems a bit off:

https://web.archive.org/web/20161206230108/https://s3-media4.fl.yelpcdn.com/bphoto/TE9gh4eqh0GxLxaGZLBJ3Q/o.jpg

Context: https://www.yelp.com/biz/comet-ping-pong-washington?hrid=kKoAiTzgCmqprdcT_YyrsQ&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

Another view of the area:

https://web.archive.org/web/20161206225958/https://s3-media3.fl.yelpcdn.com/bphoto/aub9s5l-FoVb8kCjOs_EAQ/o.jpg

Context: https://web.archive.org/web/20161206225831/https://www.yelp.com/biz/comet-ping-pong-washington?hrid=jsmQfVWtHsMXUQ7V20wj7g&utm_campaign=www_review_share_popup&utm_medium=copy_link&utm_source=(direct)

View from the ping pong room

https://web.archive.org/web/20161206230719/https://s3-media4.fl.yelpcdn.com/bphoto/Oc9Le6AUmBMp4S3TMGxc8g/o.jpg

Context: https://web.archive.org/web/20161206230540/https://www.yelp.com/biz_photos/comet-ping-pong-washington?select=Oc9Le6AUmBMp4S3TMGxc8g