This was an 80's TV cartoon series that was a lot like Scooby-Doo. The dog characters catchphrase was something like "it's ridiculikulous" and turned invisible (when scared?).
It ran for one season consisting of sixteen episodes in 1973. It is very similar to Scooby-Doo and was created by the same production studio, Hanna-Barbera Productions. The Wikipedia plot summary mentions he can become invisible as you say (emphasis mine).
Similar to Hanna-Barbera's successful Scooby-Doo, Where Are You!, Goober and the Ghost Chasers also features a group of teenagers solving spooky mysteries with their Afghan Hound-like dog Goober. The Ghost Chasers use their equipment from the Apparition Kit (like the Specter Detector, the Poltergeist Powder, etc.) when it comes to determining whether the ghost is real or not. The major differences were that the ghosts they eventually find are real and would help in defeating the fake ghosts. Some of those people behind the mask of some fake ghosts are not criminals. Goober had the power to become invisible (but could not control it) and his closest human companion is reckless instead of cowardly. Also unlike Scooby-Doo, Goober can talk more clearly, but speaks only to "break the fourth wall" with a comment aimed at the viewers; otherwise, he merely barks.
In the intro clip he also utters "it's ridiculikulous" around 25 seconds in.
This YouTube clip shows Goober becoming invisible whilst still wearing a hat at around 1 min to 1 min 10 secs.
It's Goober And The Ghost Chasers: Wikipedia article
I remember it being shown on British TV in the mid-to-late '70s (although it may have been repeated in the '80s). The phrase "it's ridiculiculiculous" stuck in my memory ever since!