It's difficult to remember now why Jasper Johns's flag paintings, Andy Warhol's Campbell soup cans and Roy Lichtenstein's comic strip panels were so startling when they first appeared. At the time, these subjects, much like landscape in early 19th-century France, were not considered "exalted" enough for art. But for the past half- century, the popular vernacular of comics, cartoons, advertising and television has provided a rich source of imagery for artists as diverse as Sigmar Polke, Peter Saul, Takahashi Murakami and Barry McGee. Now Houstonians Greg Donner and Patrick Phipps are pursuing pop in two very different ways.

Greg Donner may be one of this city's best painters-you-never-heard-of, and his first solo show, "Gravitate," at ArtScan Gallery/Rudolph Projects, is a beauty. This thirtysomething refugee from Buffalo's winters makes colorful, mid- to large-size acrylic paintings, with rolled or airbrushed grounds populated by found images from newspapers, coloring books, clip art collections, children's drawings, cereal boxes and even "gerbils," the little symbols his ancient printer produces when it garbles a job. Most of the grounds are flat fields of a single color, while those that have been airbrushed modulate between two or more colors. In some instances, the ground is something more than support. In Hippo (2003), it resolves into a beautifully realized splash of water, rendered in purple and teal; above and off to the right, a blue cartoon hippo (with lovely green eyes) is suspended upside down, as though it may have caused the splash as it flipped out of the water.

Not all of Donner's paintings are so whimsical. In fact, Oil Tanker (2003) is disconcertingly topical. The ghostly titular silhouette, outlined against a fiery background, occupies a square set against a dark green field; a toy soldier and toy airplane hover around it, a cartoonish germ-monster squats above, and two liquidy splashes, of a lurid green and yellow you just know is toxic, complete the composition. And Family History (2001) certainly isn't telling all it knows. Consisting of a piggy bank (a recurring motif throughout the show), a child's drawing of a Pilgrim, the Quaker Oats guy, a family unit silhouette from some demographic chart, a sketchy scene from a Western and a few other more obscure icons, it seems concerned with security and promises ("Nothing is better for thee than me"). But the painting is oblique and reserved.

Some might find this body of work calculated, or lacking a certain emotional quality, because of the reliance on found imagery and the exceptional polish of the paintings. (Such a reaction would not be too different from some initial criticisms of the pop artists.) The answer to this criticism is Raining Candy (2003), in which giant Life Savers and glistening raindrops fall on a moon-eyed clip-art calf frolicking against a deep blue ground. Inspired by a drawing, hanging just to the right of the painting, by a ten-year-old boy whom the artist tutored until the family moved away, it may be one of the sweetest, most optimistic paintings I've ever seen.

At Mixture Contemporary Art, Patrick Phipps has mounted a show titled "Friends of Club Monster Island," an exhibit comprising drawings, paintings, T-shirts and a poster. Why Club Monster Island? Well, the artist got here first (as they usually do), and he can name it whatever he wants. Since Phipps pursues a range of artistic practices, from painting to sculpture to 'zines to music (as DJ TrickHips) to T-shirts, he wanted an umbrella under which to collect these diverse but related endeavors.

In the show's drawings and paintings, Phipps pursues a kind of pop surrealism. His drawings are stream-of-consciousness, incorporating semi-recognizable cartoon figures, often produced at his job (if you or I did these, they'd be called doodles, because they'd be a lot simpler). In one of the most involved drawings, FOCMI is King (2002), the centerpiece, as it were, is a note regarding a customer calling for a book (Phipps is the manager of the Menil Collection's bookstore). Unlike the rest of us, who'd probably waste what was left of the paper, Phipps has filled it in with the word "obey" in orange and red block letters, other book titles, Web addresses and, for good measure, a fish-critter and a man-critter. What's it all mean? Who knows -- but it's a hell of a lot of fun to ponder. (Among other possibilities, Phipps's drawings further Robert Rauschenberg's expressed desire to eliminate the divide between art and life.)

One of the most curious pieces in the exhibit is a wall sculpture, of hydrocal, wood and gouache, titled The Old Salisbury Steak Mine (Imagineering) (2003). If you've ever wondered where "mystery meat" came from, this sculpture provides a perfectly plausible explanation. The sculpture presents the entrance to the mine, an enterprise one might imagine Yosemite Sam presiding over, and, given the pun in the title, Warner Bros. might want to "stake" a claim to it.

If you think you detect a double entendre in the acronym of Phipps's exhibit, FOCMI, you are correct. It's intended as both a self-deprecating expletive and (since Phipps is a bit of an Anglophile) an expression that Brits employ when surprised. And that second meaning is perhaps an appropriate place to end. The element of surprise is important in the work of both of these artists: in Donner, the surprise of juxtaposition; in Phipps, the surprise of spontaneous invention. And surprise always stirs us to wonder.

"Gravitate" Through April 12 at ArtScan Gallery/Rudolph Projects, 1113 Vine, 713-224-7722.

"Friends of Club Monster Island" Through April 12 at Mixture Contemporary Art, 1709 Westheimer, 713-520-6809.