Fireflies.
There are a total of 15 fireflies to collect in Finding Teddy, you do not have to collect all of them in the same playthrough, but you must collect them all on the same save file to earn the Firefly Collector achievement. If you start a new save file, that save will not carry across your collected fireflies.

If you are having problems finding them or want an easy ride, after you complete your first playthrough and start the New Game +, enable the spider mask and this will make all fireflies constantly visible.

I have also added time markers for all of the fireflies on my video walkthrough below. Be aware that the numbering of the flies is just a tally in the order I collected them and not or the order they appear in the collectable chart.

Gallery Pictures Collectables.
There are 23 pictures to unlock, some appear to have certian requirements to unlock others perhaps do not. As such I have noted the exact point where the pictures unlocked for me.

The first unlocked just after entering the wardrobe at the start of the game.

One was unlocked each time I collect a firefly.

One unlocked when I passed through the door secured by a yellow padlock passing into the second stage.

One unlocked after passing the snake and entering the third stage of the game.

After passing the snake and starting the 3rd stage, I saved my game, exited and some time later loaded my game back up and another picture unlocked as I did.

One unlocked when I entered Tarant's lair and I finished my first play through with 20 pictures.

On my second playthrough (NG+) one unlocked as I went to the right from the starting point to the area with the yellow fruit on the floor.

One unlocked when I played "sorry" at the graveyard and the musician achievement popped here, despite only having only recorded collecting 22 pictures, I can only assume another picture unlocked somewhere while not recording/AFK.

At the end of your NG+ (second playthrough) if you only have 22 pictures, just load up your save again and the 23rd should unlock just after you pass through the wardrobe.

Video contains...
@1m17s = Blobbed achievement.
@ 2m40s = Firefly collectable #1.
@ 3m00s = Firefly achievement.
@ 3m24s = Firefly collectable #2.
@ 3m59s = Monstered achievement.
@ 5m20s = Firefly collectable #3.
@ 5m48s = Wasped achievement.
@ 6m30s = Firefly collectable #4.
@ 10m06s = Bzzzz achievement.

Video contains...
@ 1m00s = First stage point of no return.
@ 1m17s = Firefly collectable #5.
@ 2m11s = Firefly collectable #6.
@ 2m30s = Firefly collectable #7.
@ 3m11s = Firefly collectable #8.
@ 4m07s = Firefly collectable #9.
@ 4m42s = Spidered achievement.
@ 5m12s = Firefly collectable #10.
@ 7m09s = Meow achievement.
@ 7m49s = Crocodiled achievement.
@ 13m25s = Firefly collectable #11.

Video contains...
@ 0m03s = Snaked achievement.
@ 0m12s = Second stage point of no return.
@ 1m17s = Firefly collectable #12.
@ 1m17s = Firefly collectable #13.
@ 1m17s = Firefly collectable #14.
@ 6m15s = Baby Sitter achievement.
@ 7m20s = Spidered. Again ! achievement.
@ 1m17s = Firefly collectable #15.
@ 8m53s = Firefly Collector achievement.
@ 11m42s = Taranted achievement.

Video contains...
@ 1m50s = Teddy's Saviour achievement.
@ 2m04s = NG+ Start.
@ 12m50s = First stage point of no return.

Video contains...
@ 4m09s = Who's Your Daddy? achievement.
@ 4m09s = Musician achievement.
@ 4m09s = Artwork Collector achievement.
@ 4m09s = R.I.P. achievement.
@ 8m00s = Second stage point of no return.

Video contains...
@1m24s = Nyanyanyanya achievement.

For anyone with problems viewing the embedded videos in this guide (such as those in China having to use a VPN to watch videos on YouTube) here's a link to the playlist...
https://www.youtube.com/playlist?list=PLgrKGjfHCc0hpB7jw1i2asG9o0-IlL1w_

I hope you found this guide of help, all comments, suggestions and criticism (constructive) is gratefully received.

An A to Z list of my Steam achievement guides and walkthroughs can be found @ https://cs2bus.com/sharedfiles/filedetails/?id=1502405720
If you would like to get a notification in your activity feed when I post a new guide, just click the "follow anrkyuk" button on my profile guide list...
https://cs2bus.com/id/anrkyuk/myworkshopfiles/?section=guides