CT Lac is a star I stumbled over several weeks ago while looking for examples of long-period pulsating variables. It's a semiregular (SRa) and carbon star with very long period of 562 days. If you look at the last ten years or so of data, you'll find that the amplitude has appeared to decrease and, more strikingly, the maximum magnitude has also appeared to decline. The AAVSO light curve only goes back to the late 1960s, but in that time at least there's no evidence of similar behavior.
It's possible the star is doing something similar to the Miras and semiregulars with long secondary periods (like RU Vir ), but there's no way to tell that without additional multiwavelength observations and/or spectra.
This star isn't well observed and observations appear to be very sparse even though Lacerta is well placed right now. If you are looking for interesting objects to mix up your observing program, this might be a good one to add to your list (both visual and CCD).