Oh My Cthulhu - a replacement for "Oh My God" (aka "omg") for those who prefer one (for whatever reason, including you're not religious or you're too religious to feel comfy using "god"). OMC evokes the great chaotic deity from Lovecraftian lore. Often used humorously.

Additional exclamation replacements include:
"Cthulhu's spawn!" instead of: "Jesus Christ!"
"Praise the Chaotic One" instead of: "Praise the Lord"

OTARA MILLIONIARS CLUB
An R and B group that started in otara, Auckland,New Zealand.Then moved on to the States.Paul Fueamana(bad spelling?)and co.His brother(Phil) just died Circa March 2005 rip.Best known for 'How Bizarre'.

Basically a replacement for OMG, but instead of god at the end I thought a more iconic figure:Charizard.
The meaning is can range from surprise to 'that's just awesome'.

O.M.C=Over mature child
Used to poke fun at someone who has a mature face but likes things normally associated with children or acts childishly.

Off my charts

Acronym of Oh My Chad, a variation of oh my god, originating in the Disney channel series Sonny With a Chance. Commonly used by screaming fangirls.

Acronym for old married couple. Used to describe a young-ish (16-35 year old) couple that has a tendency to behave as if they've been married for 40 years.