Basically, we wanted a little statue commemorating the first Linux PC cluster supercomputer, so the idea was to symbolize the cluster network by putting classic "mind transfer" caps on a pair of Tux, the Linux penguin. The nicest 3D Tux we found for that purpose was Thing 118892, which we tweaked a bit and added the caps to. If separated into front and back halves, this Tux is printable without supports... and our refrigerator magnet only needs the front half.
Our prints were made using 0.25mm extrusion of PLA at over 100mm/s with 2 walls and 5%-10% fill on a MakerGear M2. There were no difficult-to-print areas, although with such low fill percentages one has to beware unfortunate alignments of the fill matrix that could result in minor holes in the flat portion of the base between the letters (at least when slicing with cura).
The magnets are cut from a roll of 1"-wide self-stick magnetic tape and inserted into the cavities in the backs of the penguins after printing. To help them stay in place, we pressed them into hot glue laid into the cavities... but even that doesn't work perfectly. Oh well; many refrigerator magnets loose their magnets too easily. ;-)
For prints using dark colors, the text on the base and penguin chests was simply painted with a white latex paint... which sticks well enough thanks to the surface roughness of the PLA, although one could perhaps do even better by lightly sanding those surfaces first. We also printed some of these in white PLA, in which case a permanent marker worked fine to dye the top surfaces of the letters.