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The high spatial resolution of the Hubble Space Telescope (HST) has led totremendous progress in many areas of astronomy. The ability of the HST to peerinto the bright inner regions of galaxies and distinguish between globularclusters (GCs) and background objects has been particularly beneficial to thestudy of clusters. But the very virtue of the HST that has been an asset tosuch research can be its pitfall if the consequences of superior angularresolution are not considered in detail. Recent HST studies show a small, butconsistent, color-magnitude correlation in the metal-poor halo GCs of nearbygalaxies. This `blue-tilt' has been interpreted as a mass-metallicityrelationship, implying self-enrichment in the higher mass GCs. We show that the`blue-tilt' is likely the consequence of a small, but measurable with HST,mass-size relationship in GCs. The combined effects of Poisson noise andsurface brightness fluctuations can explain other apparent correlations of the`blue-tilt' with environment. Some HST based studies have similarly suggestedthat the mean metallicity of the blue, metal-poor, halo clusters increases withhost galaxy mass, indicating that GC metallicity is linked to the size of thehost galaxy halo. We show that this correlation is also likely due to theeffects of GC size in high resolution HST images. We also point out that thepresumed fundamental plane of GCs itself varies with galactocentric distancedue to GC size trends and ultra compact dwarfs may simply reflect the tail ofthe globular cluster distribution.

Observational Biases Masquerading as Cosmological Effects? A Cautionary Tale about Blue Tilts and Other Trends in Globular Cluster Systems