Many of the characters in BFDI, depending on the object, have had their own 'OMG' moments in which they state "Oh my" and then something relevant to their "God", which is something related to their object form, for example Pin's "god" is a Pin Factory, which created her.
Several characters may use the regular "Oh my God/gosh" instead of a thematic variant. These characters include Tennis Ball, Stapy, Bubble (though pronounced "goish"), Bomby, Eraser, Yellow Face, Nickel, and Pen
Some characters have 'WTH' (what the heck) moments, like Snowball (What The Flake) and Match (What The Woodsicle).
Book's OMG moment is "Oh my Word", which was used twice.
Bubble's OMG moment is "Oh my Bubble Blower!", sometimes shortened to "OMBB!"
In Season 1 Coiny's OMG moment was "Oh my Midge" or OMM.
Coiny's OMG moment was said once in Why Would You Do This on a Swingset as "Oh My Mint!" or OMM for short.
In Four Goes Too Far it was considered to have Donut say something along the lines of "Oh Dear God", but was replaced with "This can't be real" because according to Cary they didn't want to have God in a BFB episode.
Firey's OMG moment is "Oh my Oxygen!", used once after getting barfed on.
In BFDI Is Back, when he discovers the release date for IDFB 1, he says, ”Oh my Spark!”
In other episodes, Firey says "Oh my gosh".
FlowerIn Insectophobe's Nightmare 2, Flower states her OMG as "Oh my Gardener!"
Fries' OMG moment is "Oh my Potatoes", used twice.
In Welcome Back, Fries's other OMG moment is "Oh my tater", used once.
Gelatin's OMG moment is "Oh my collagen", used once in a video including BFDIA 6 deleted scenes.
Also in Barriers and Pitfalls Leafy said "OMZ", no one knows what it stands for though.
In Cycle of Life, she may have said "OMT", which may mean "Oh my Tree" but it may have just been an "OMG". Closed Captions say "OMG", but they weren't set by hand.
Match is the first to say OMG or a related word like OMQ, OMW, OMZ more than 10 times even 20 times.
Pencil has an OMG moment, and it is "Oh my Tree" because wood comes from trees, and Pencils are made with wood. It has been used twice in both the BFDIA 6 Deleted Scenes video as well as Welcome Back.
Snowball's OMG moment was said at the biggest and final rejoining ceremony of Season 1 as "Oh my Snowflake!"