Imagine a Funny Venn Diagram

Eek the Cat genuinely wants to help ("It never hurts to help!" is his catchphrase, even) and does so honestly and earnestly. Unfortunately, chaos inevitably results from circumstance, poor risk assessment, and the fact that he's got a SUCKER sign on his forehead visible from space.
Felix (well, the real Felix) may try to help, but likely because circumstances have forced it or the entroubulated's interests coincide with his own. Chaos results because of inconsistent judgement, Felix's inherent greed and trollishness, and the fact that he inhabits an even weirder, less predictable world than Eek does. In short, Felix getting involved is a lot closer to real-life "cat help", as anyone with a computer and a cat can attest.

Eek has considerable strength of character, but is hampered by a lack of power within his environment. Felix has considerable power in his environment, but is hampered by character faults. Despite not being a cat, Uncle Grandpa exists near the midpoint of the two, leaning Felix. He honestly and earnestly tries to help, but has inconsistent judgement and troll tendencies that escalate (or cause) the issue. Like Eek, he's willing to forgo self-interest and sustain harm to aid a stranger - although with Uncle Grandpa his magic-powered assistance only becomes crucial after interjecting himself into the situation in the first place. Even Eek wasn't beyond that, however, often enough inadvertently "helping" someone accomplish something clearly destructive then being forced to "help" deal with the results.

Uncle Grandpa seems to cause these situations more through Eek-like lack of awareness than greed or malice, but it can be argued his desire for "fun" (see 'Uncle Grandpa Sitter') and obsession with favourite foods are responsible for his lack of awareness regarding consequences. Of course, Felix the Cat is seldom actively malicious, but similarly enslaved by his passions. Like both Eek and Felix, Uncle Grandpa's results are unpredictable in part due to the utter strangeness of his surroundings - but he's closer to the Felix side in his interaction with them. Felix is a creature of chaos, Eek is a non-native in chaos. Uncle Grandpa is without question the former.



PS: Enjoy being in TV Tropes forever! The Troper Trapper strikes again! See you in the rabbit hole...