Here's a pair of scenarios, either of which might form the basis for a fun picture:
1a. Sam, Alex and Blossom huddle in the middle of the frame, side by side by side, bound by Chewy's leafy tendrils and totally helpless. Chewy looms menacingly overhead, a sadistic smirk on his face, as he mercilessly works their most ticklish spots (special attention to the bare soles of their feet, which face the viewer).
or
1b. Same scenario as above, but only one of the girls receives Chewy's special attention. The other two (tightly secured) watch in dismay, knowing that their turn will soon come!
2. Chewy is in the center of the picture, hoisting Blossom high over his head, tickling her into shrieking hysteria. Sam and Alex wrestle with the mad plant, striving to rescue their tormented partner. Chewy effortlessly holds them at bay, using stray vines to soundly tickle them as well, just for good measure.
C'mon, guys! Don't let me have all the fun! Let's hear some further suggestions!